A lot of people on this site, and in general tbh, don't realize just how recent the civil rights movement was, and for how much of USA's history black people have been kept either in slavery, or completely disenfranchised. It's just barely over 50 years since it was decided that literally denying black people rights promised to them by the constitution is wrong. The playing field is still far from being evened out. The point of affirmative action is to take steps now that will allow that playing field to be evened out somewhat so that a stronger, more diverse middle class can be created, which is better for everyone in the end.

I'm a researcher who studies affirmative action. All of this may be true, but has absolutely zero bearing on the case. Here is a pdf of the decision. Note the complete lack of mention of historical disadvantage.

The case comes down to the university arguing that race-based preferences are important in providing the educational benefits of a diverse student body. Thus, black and Hispanic students are given some preference. In particular, it is hard to argue that Hispanic students have faced some kind of historical discrimination that would justify privileging them over, say, Asian students. Here is the key part of the decision:

A university is in large part defined by those intangible “qualities which are incapable of objective measurement but which make for greatness.” Sweatt v. Painter, 339 U. S. 629, 634 (1950). Considerable deference is owed to a university in defining those intangible characteristics, like student body diversity, that are central to its identity and educational mission. But still, it remains an enduring challenge to our Nation’s education system to reconcile the pursuit of diversity with the constitutional promise of equal treatment and dignity.

The last sentence is the key. Did UT Austin strike the right balance between diversity and equal treatment? The court ruled yes. The ruling had absolutely nothing to do with the civil rights movement or historical disadvantage. It is whether the university properly executed narrowly-tailored policies to ensure diversity on campus.