That was absolutely the type of game that Texas either loses or has to bat down passes at the end to preserve a win.
The UTSA QB and his receivers can win games largely by themselves. Their OL was patchwork, and the Texas defense made it even more so, but it didn't matter. He got the ball out quick and on target! That first drive took over 8 minutes, as UTSA kept just barely squeaking 3rd downs over the line. Some weak tackling and failure to rally to the ball by the Texas defense helped that out a lot. I'm sure that film will be reviewed.
The beginning game plan was to see if Bijan could simply run off tackle for a win. UTSA knew that plan, and stacked up to see what would happen next. Fair play to them. Texas, unlike years past, mixed in just enough short yardage passing to push the defense back. That let the OL breathe enough to get a running game going.
In the end, Texas had more athletes for longer. In a game that was more mental than anything else, Texas finally landed the kill shot when they had a plucky fighter on the ropes (after having the 'targeting' statue rewritten for dramatic effect).
Jeff Traylor got everything out of his team, who were more than willing to celebrate a win over Texas. As you'd expect, Texas had more athletes to throw at the problem.