Because they were clearly better all season. Like I said, that spring "championship" was fluky nonsense. Depending on the restrictions still in place, some teams couldn't even practice regularly. That SHSU team was overrated all year. They only played one team that ended up top 25 or better all year and only barely beat them 21-20. People like me were calling them out as soon as the bracket was released.
I'm not trying to take away from what the cats did, they beat all the teams they needed to, but their side of the bracket was MUCH easier than the other.