I’m guessing they went back to the drawing board several times - probably because they felt their sequel wasn’t really as evolved or as fun as what they had hoped it would be, so they shifted I’m guessing from their overhead view to the behind the player 3rd person style game we know now at some point after churning at it for a couple years at least…
Like you know that Doom 2016 was the 3rd complete from scratch redo from what they originally started working on after Doom 3, right?
This sort of thing sometimes happens in creative projects; like when you hear a movie took like 7 years to make, it’s not necessarily that they literally shot scenes every week for the same film that whole time. It’s that the project was shelved, or they changed directors, or the studio lost interest for a while or they got a new script or something.