Snickersnack: I'm afraid you're mistaken. Mouse aiming was most definitely a thing on PC FPS going back to at least Wolf3D. You may be thinking about freelook which didn't catch on until some time after Quake*.
Here's someone asking John Romero about the subject:
https://twitter.com/romero/status/569772884089901056 Yes, you proved 2 things:
a) M+K combo is more efficient, which is something I never disputed
b) It wasn't until Quake that design around freelook (you're right) started emerging. It's quite logical - even in 1993, usage of mouse wasn't quite as widespread as to rely on your customers both having it and being comfortable with using it to play videogames. I'd hazard a guess that most gamers had their mice even back then, but I don't really have data to back that up.
Snickersnack: We may have a disagreement about what DOOM is so I'm not going to pick on your DOOM slow pacing comment/ heresy. ;)
Look, I love Doom. I still play it - admittedly with Brutal Doom mod, which I would never touch without a mouse since it removes autoaim (or, to put it better, which I set to remove autoaim). Nonetheless, it's just not nearly as fast-paced as games designed around the use of mouse control, such as Painkiller, later Tribes games, Unreal Tournament, Quake 3 etc. And it really can't be - due to hitscan weaponry, unless you know the game very well, rushing ahead into a pack of monsters has a tendency of getting you killed.