College football programs have been around for 100+ years, you think they'd dry up and disappear in 2 years because 1% of the athlete pool was recruited to play in a new league? Doubtful. People follow college football for the uniforms, not for the players, anyway IMHO.
And one thing being overlooked here is that, while the players aren't paid a salary, they benefit from cutting edge training and nutrition and, in most cases now, luxury accommodations. The XFL is going to need a whole lot more than $100M to provide anything even comparable to what these players get from Power 5 schools in terms of training and exposure.
Plus, even if one thinks the education/degree these kids get the opportunity to pursue is a sham, by going to these colleges they get access to a vast network of alums and boosters. That tends to set up the majority of kids who don’t land in the NFL. Financial firms are loaded with ex-D1 football players who never sniffed the NFL, for example.