This is an easy one if one steps back to look at the Big Picture.
The correct answer is Sean McVay.
Want evidence that the team flows from Sean McVay? In 2016 Rams finished 4-12 with a pretty damned good roster, including AD, btw.
In McVay’s rookie season Rams finished 11-5, won their dividiom, and O went from worst to first, literally.
I love AD to death, too, but there’s no doubt in my mind as to which person is most critical to Rams success.
Les Snead would be #2, incidentally, by that same logic.
Stafford would now be #3 because he’s the starting QB.
AD, the certain future HOFer, would be #4.
I’m gonna duck behind my couch now. Lol.