Kanjani Eight was the combination of the four top leading Kansai Juniors of the "Junior golden age" and the newly popular V. West (Five West), a rock band Kansai Junior unit. Prior to the creation of the group, Subaru Shibutani, Yuu Yokoyama, Shingo Murakami, and Ryo Nishikido were one of the top leading juniors of the time, headlining many Junior hosted programs and acting in dramas. After the debuts of Arashi and Tackey & Tsubasa, the golden era was suddenly coming to an end and so was their popularity. By the year 2001 all their activity had slowed down to magazine photoshoots.  On the contrary, a new Kansai Junior unit named V. West was taking off in popularity, more so than their eastern counterpart FiVe. The group consisted of Ryuhei Maruyama, Shota Yasuda, Hiroki Uchi, Kiyohito Mizuno, and Tooru Imayama. The group became so popular that by 2001 they had their own television show, Weekly V. West. But, when Mizuno and Imayama left Johnny's & Associates, worry had begun to creep within unit as to their fate within the talent agency.  In 2002, after the end of Weekly V. West, a new program was created to replace it on Kansai TV Channel 8 entitled J3Kansai (pronounced as J Cube Kansai). This show brought together the top leading Kansai Juniors of the golden age and V. West creating the new Junior group, Kanjani, a portmanteau of the words Kansai Johnny's. With the success of the stage play, Another, the group became official garnering the name Kanjani Eight. The "8" stood for the channel that the show J3Kansai aired on. Tadayoshi Ohkura had been added to the group as a drummer and then as an official member in the 12 episode finalizing the group as an eight-member group.  Kanjani Eight, as a newly formed group, held their first concert in December 2002, titled " Kanjani Eight Xmas Party 2002 ". This concert ended up becoming a yearly tradition before ending in 2005. It was also the birthplace of the group's signature act, Kanjani Sentai Eight Ranger.  In 2003, Kanjani Eight members Nishikido and Uchi were called to go to Tokyo to become a part of NEWS, another Johnny & Associates group.

Answer this question "Why did they combine?" by extracting the answer from the text above.
Kanjani Eight, as a newly formed group, held their first concert in December 2002,