Some context: A Night at the Opera is the fourth studio album by the British rock band Queen, released on 21 November 1975 by EMI Records in the United Kingdom and by Elektra Records in the United States. Produced by Roy Thomas Baker and Queen, it was the most expensive album ever recorded at the time of its release. The album takes its name from the Marx Brothers film of the same name, which the band watched one night at the studio complex when recording. A Night at the Opera incorporates a wide range of styles, including ballads, songs in a music hall style, hard rock tracks and progressive rock influences.
"Death on Two Legs" can be referred to as Freddie Mercury's hate letter to Queen's first manager, Norman Sheffield, who for some years was reputed to have mistreated the band and abused his role as their manager from 1972 to 1975. Sheffield denied the allegations in his 2013 autobiography entitled "Life on Two Legs: Set The Record Straight", and referred to copies of the original 1972 management contracts between Sheffield and Queen, which were included in the book as proof of his defence. Though the song never makes direct reference to him, after listening to a playback of the song at Trident Studios during the time of album release, Sheffield was appalled, and sued the band and the record label for defamation, which resulted in an out-of-court settlement, but also confirmed his connection to the song.  During live performances, Mercury would usually rededicate the song to "a real motherfucker of a gentleman", although this line was censored on the version that appeared on their Live Killers album in 1979. Other than on the live album, he said it was dedicated to a "motherfucker I used to know".  In the Classic Albums documentary about the making of A Night at the Opera, Brian May stated that the band was somewhat taken aback at first by the bitterness of Mercury's lyrics, and described by Mercury as being "so vindictive that he [May] felt bad singing it". After the song came together, it was agreed that the "author should have his way", and the song was recorded as written.  As with "Bohemian Rhapsody", most of the guitar parts on this song were initially played on piano by Mercury, to demonstrate to May how they needed to be played on guitar. "Death on Two Legs" remained on the setlist until, and well into, The Game Tour in 1980, and was then dropped. However, the piano introduction was played during the Hot Space and Works tours.
Was this popular?
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Some context: Maelgwn Gwynedd (Latin: Maglocunus; died c. 547) was king of Gwynedd during the early 6th century. Surviving records suggest he held a pre-eminent position among the Brythonic kings in Wales and their allies in the "Old North" along the Scottish coast. Maelgwn was a generous supporter of Christianity, funding the foundation of churches throughout Wales and even far beyond the bounds of his own kingdom. Nonetheless, his principal legacy today is the scathing account of his behavior recorded in De excidio
In his work On the Ruin and Conquest of Britain written c. 540, Gildas makes an allegorical condemnation of 5 British kings by likening them to the beasts of the Book of Revelation, 13-2: the lion, leopard, bear, and dragon, with the dragon supreme among them. He says that Maelgwn is the "dragon of the island", and goes on with a litany of moral accusations, in the process describing him almost as a regional high king over the other kings (the power-giving dragon of the Apocalypse). The Isle of Anglesey was the base of power of the kings of Gwynedd, so describing Maelgwn as the "dragon of the island" is appropriate.  Gildas restricts his attention to the kings of Gwynedd (Maelgwn), Dyfed (Vortiporius), Penllyn (probable, as its king Cuneglasus/Cynlas appears in royal genealogies associated with the region), Damnonia/Alt Clud (Constantine), and the unknown region associated with Caninus. The Welsh kingdoms are all associated with the conquest of the Gaels by Cunedda, while Alt Clud had a long and ongoing relationship with Gwynedd and its kings.  In the course of his condemnations, Gildas makes passing reference to the other beasts mentioned in the Apocalypse, such as the eagle, serpent, calf, and wolf. The reason for Gildas' disaffection for these individuals is unknown. He was selective in his choice of kings, as he had no comments concerning the kings of the other British kingdoms that were thriving at the time, such as Rheged, Gododdin, Elmet, Pengwern/Powys, or the kingdoms of modern-day southern England. That he chose only the kings associated with one king's pre-eminence (Maelgwn, the "dragon") suggests a reason other than his claim of moral outrage over personal depravity. Neither outrage nor a doctrinal dispute would seem to justify beginning the condemnation of the five kings with a personal attack against the mother of one of the kings, calling her an "unclean lioness".
Was there any speculation why he made this comments?
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suggests a reason other than his claim of moral outrage over personal depravity.