The population of Texas is 12.8% black, slightly lower than the US average of 13.4%. For the stands to be mostly black people at a public event (in most areas where they represent a small share of population) would mean that the event was overwhelming of interest to black people and not so much to others. A crowd that looks like the demographics of the region surrounding it is healthy, not a sign of racism.
As for college football, while black athletes are “over represented” for their share of the population, according to the NCAA they are still a bit less than half the number of players. There is no shortage of white people who want to play football and are willing to risk injury to do so.
The over representation of black people in high-level athletics is meritocratic: they get there by being the best.
There is a legitimate question as to why many in the black community pursue sports so seriously, when the odds of a successful career are terribly low compared to more mundane things like accounting or whatever. I am not an expert, but my understanding is this is more a factor of black people disproportionately living with poor performing schools and structural poverty, such that children have see fewer role models that “look like them” outside of sports, which in turn facilitates the perception they have a better chance of success in sports than in other fields, even though that’s generally not true.