On this idea of "how many athletes would be accepted into these schools on their academic merits" question...
See, I always felt that it was a feature, not a bug, of American higher education, that students that weren't exceptional academically are granted opportunities to associate, network, and learn alongside traditionally academically gifted students because they brought talent of a different stripe (athletics, music, drama, other language expertise/world perspectives, etc.) to enrich the school community and enhance the pursuit of excellence of all different manifestations of human ability.
Maybe that's naive or too optimistic, but when people talk about diversity being desirable... this is all a part of it.