Background: The Spice Girls are an English pop girl group formed in 1994. The group originally consisted of Melanie Brown ("Scary Spice"), Melanie Chisholm ("Sporty Spice"), Emma Bunton ("Baby Spice"), Geri Halliwell ("Ginger Spice"), and Victoria Beckham, nee Adams ("Posh Spice"). They were signed to Virgin Records and released their debut single "Wannabe" in 1996, which hit number one in 37 countries and established them as a global phenomenon. Their debut album Spice sold more than 31 million copies worldwide, becoming the best-selling album by a female group in history.
Context: While on tour in the United-States, the group continued to record new material and released a new song, "Goodbye", before Christmas in 1998. The song was seen as a tribute to Geri Halliwell, and when it topped the UK Singles Chart it became their third consecutive Christmas number-one - equalling the record previously set by the Beatles. Later in 1998, Bunton and Chisholm appeared at the 1998 MTV Europe Music Awards without their other band members, and the group won two awards: "Best Pop Act" and "Best Group" for a second time. In late 1998, Brown and Adams announced they were both pregnant; Brown was married to dancer Jimmy Gulzer and became known as Mel G for a brief period. She gave birth to daughter Phoenix Chi in February 1999. One month later, Adams gave birth to son Brooklyn, whose father was then Manchester United footballer David Beckham. Later that year, she married Beckham in a highly publicised wedding in Ireland.  The Spice Girls returned to the studio in August 1999, after an eight-month recording break to start work on their third and last studio album. The album's sound was initially more pop-influenced, similar to their first two albums, and included production from Eliot Kennedy. The album's sound took a mature direction when American producers like Rodney Jerkins, Jimmy Jam and Terry Lewis came on to collaborate with the group. In December 1999 they performed live for a UK-only tour, Christmas in Spiceworld, in London and Manchester, also showcasing new songs from the third album. During 1999, the group recorded the character Amneris' song "My Strongest Suit" in Elton John and Tim Rice's Aida, a concept album which would later go on to fuel the musical version of Verdi's Aida. The band performed again at the 2000 Brit Awards, where they received a Lifetime Achievement Award. Despite being at the event, Halliwell did not join her former bandmates on stage. In November 2000, the group released Forever. Sporting a new edgier R&B sound, the album received a lukewarm response from critics.  In the US, the album peaked at number thirty-nine on the Billboard 200 albums chart. In the UK, the album was released the same week as Westlife's Coast to Coast album and the chart battle was widely reported by the media, where Westlife won the battle reaching number one in the UK, leaving the Spice Girls at number two. The lead single from Forever, the double A-side "Holler"/"Let Love Lead the Way", became the group's ninth number one single in the UK. However the song failed to break onto the Billboard Hot 100 singles chart stateside, instead peaking at number seven on the Bubbling Under Hot 100 Singles. "Holler" did peak at number thirty-one on the Hot Dance Music/Club Play chart in 2000. The only major performance of the lead single came at the MTV Europe Music Awards on 16 November 2000. In total, Forever achieved only a fraction of the success of its two best-selling predecessors, selling five million copies. In December 2000, the group unofficially announced that they were beginning an indefinite hiatus and would be concentrating on their solo careers in regards to their foreseeable future, although they pointed out that the group was not splitting.  The phrase "girl power" put a name to a social phenomenon, but the slogan was met with mixed reactions. The phrase was a label for the particular facet of post classical neo-feminist empowerment embraced by the band: that a sensual, feminine appearance and equality between the sexes need not be mutually exclusive. This concept was by no means original in the pop world: both Madonna and Bananarama had employed similar outlooks. The phrase itself had also appeared in a few songs by British girl groups and bands since at least 1987; most notably, it was the name of British pop duo Shampoo's 1996 single and album, later credited by Halliwell as the inspiration for the Spice Girls' mantra.  However, it was not until the emergence of the Spice Girls in 1996 with "Wannabe", that the concept of "girl power" exploded onto the common consciousness. The phrase was regularly uttered by all five members--although most closely associated with Halliwell--and was often delivered with a peace sign. The slogan also featured on official Spice Girls merchandise and on some of the outfits the group members wore. The Spice Girls' version was distinctive. Its message of empowerment appealed to young girls, adolescents and adult women, and it emphasised the importance of strong and loyal friendship among females.  In all, the focused, consistent presentation of "girl power" formed the centrepiece of their appeal as a band. Some commentators credit the Spice Girls with reinvigorating mainstream feminism--popularized as "girl power"--in the 1990s, with their mantra serving as a gateway to feminism for their young fans. On the other hand, some critics dismissed it as no more than a shallow marketing tactic, while others took issue with the emphasis on physical appearance, concerned about the potential impact on self-conscious and/or impressionable youngsters. Regardless, the phrase became a cultural phenomenon, adopted as the mantra for millions of girls and even making it into the Oxford English Dictionary. In summation of the concept, author Ryan Dawson said, "The Spice Girls changed British culture enough for Girl Power to now seem completely unremarkable."  The Spice Girls' debut single "Wannabe" has been hailed as an "iconic girl power anthem". In 2016, the United Nations' Global Goals "#WhatIReallyReallyWant" campaign filmed a global remake of the original music video for "Wannabe" to highlight gender inequality issues faced by women across the world. The video, which was launched on YouTube and ran in movie theatres internationally, featured British girl group M.O, Canadian "viral sensation" Taylor Hatala, Nigerian-British singer Seyi Shay and Bollywood actress Jacqueline Fernandez lip-syncing to the song in various locations around the world. In response to the remake, Beckham said, "How fabulous is it that after 20 years the legacy of the Spice Girls' girl power is being used to encourage and empower a whole new generation?"  At the 43rd People's Choice Awards in January 2017, American actress Blake Lively dedicated her "Favorite Dramatic Movie Actress" award to "girl power" in her acceptance speech, and credited the Spice Girls, saying: "What was so neat about them was that they're all so distinctly different, and they were women, and they owned who they were, and that was my first introduction into girl power."  At the height of "Spice mania", the group were involved in a prolific marketing phenomenon. They advertised for an unprecedented number of brands, becoming the most merchandised group in music history, and were a frequent feature of the global press.  According to Rolling Stone's David Sinclair, "So great was the daily bombardment of Spice images and Spice product that it quickly became oppressive even to people who were well disposed towards the group." This was even parodied in the video for their song "Spice Up Your Life", which depicts the group going around a futuristic dystopian city in a space ship surrounded by billboards and adverts featuring them. Throughout the American leg of their 1998 Spiceworld world tour, commercials were played on large concert screens before the shows and during intermissions. It was the first time advertising had been used in pop concerts and was met with mixed reactions in the music industry. Nevertheless, it opened up a whole new concert revenue stream, with music industry pundits predicting more acts would follow the Spice Girls' lead.  In his analysis of the group's influence on 21st century popular culture two decades after their debut, John Mckie of the BBC noted that while other stars had used brand endorsements in the past, "the Spice brand was the first to propel the success of the band". The Guardian's Sylvia Patterson also wrote of what she called the Spice Girls' true legacy: "[T]hey were the original pioneers of the band as brand, of pop as a ruthless marketing ruse, of the merchandising and sponsorship deals that have dominated commercial pop ever since."  The mainstream media embraced the Spice Girls at the peak of their success. The group received regular international press coverage and were constantly followed by paparazzi. Paul Gorman of Music Week said of the media interest in the Spice Girls in the late 1990s: "They inaugurated the era of cheesy celebrity obsession which pertains today. There is lineage from them to the Kardashianisation not only of the music industry, but the wider culture." The Irish Independent's Tanya Sweeney agreed that "[t]he vapidity of paparazzi culture could probably be traced back to the Spice Girls' naked ambitions", while Mckie predicted that, "[f]or all that modern stars from Katy Perry to Lionel Messi exploit brand endorsements and attract tabloid coverage, the scale of the Spice Girls' breakthrough in 1996 is unlikely to be repeated--at least not by a music act."
Question: How did they contribute to commercialization?

Answer:
At the height of "Spice mania", the group were involved in a prolific marketing phenomenon.