I don’t know the truth about it, but there have been a lot of rumors swirling around that Square-Enix forced Mankind Divided to be separated into a trilogy rather than remain a single game. Whether this was done out of generalized greed and mismanagement or because the Deus Ex team really did have an over-ambitious plan that needed to be adjusted (or some combination thereof) isn’t clear, but it certainly seems to mesh with what I’m hearing about the ending. There’s a Jim Sterling video out that is quite informative on this front.