There is one factor that hasn’t been mentioned yet that I think is worth bearing in mind. Unfortunately, it is something that the applicant has no control over, but can absolutely be the determining factor in a successful admission.
LUCK.
Yes, blind, dumb luck.
Something about your application just totally captivates a particular application reader, and maybe that person happens to be the best person in the room at advocating for their personal idiosyncratic choices.
Perhaps the major you are applying to at a particular school is having a particularly bad recruiting year, and your gender is massively underrepresented in the applicant pool. Boom, your chances just got a lot better.
Or some other institutional priority is having a down year, and you fit the bill - violin player, gymnastics background, whatever.
Most of this stuff is absolutely out of your control, and it might be the difference between success and failure. This is the main reason why some people advocate shotgunning as an application strategy - that’s really an attempt to take advantage of the luck factor.