Why is the album named 'Mercury Act 1'?

Dan Reynolds revealed that ‘Mercurial’ was the original name of the album in the NMD Deutscheland Radio interview.

Mercury album name comes from the word “mercurial”, something very volatile and subject to extreme changes, drawing on my experience with mental health struggles, as well as the genre bending Imagine Dragons style, of not choosing what genre to write it, but writing what comes to me, so ‘Mercurial’ felt fitting, as the album also swings from side to side."

However, in the Wrecked livestream premiere, Dan explained as to why they didn’t name the album ‘Mercurial’:

Yeah, mercurial was the original title, but it’s a very hard word and it’s not very visually appealing either and we really like to tie the visuals with everything and want the album to be a world on its own. So we then decided on Mercury."