“why the blinking bloop is a career in professional athletics tied to higher education anyway?”
The reasons are partly historical and partly financial. The historical part is that pro sports grew out of college sports. College sports got going back in the late 1800s. Except for baseball which was earlier, pro sports didn’t get rolling until about the 1920s and didn’t become popular until the 1940s and 50s. So over time it just naturally evolved that college sports became feeders for pro sports.
The reason why it stays this way is the finanicial part. College sports stays the main feeder for pro sports, especially the NBA and NFL, because the pro leagues want it that way. College sports functions as free minor league farm teams to the NFL and NBA and to a much lesser extent for MLB and pro golf and tennis. Since MLB developed and got big before college baseball did, MLB established and still maintains at considerable expense its own large minor league farm system to develop and season the talent. NFL and NBA gets the same thing free from the colleges. So why would they want to give that up? It’s hugely in their interest to keep the free farm system alive. The system continues because money talks, and there are billions of dollars at stake here.