And they struggled all game. It didn't hurt as much in the second half because Utah State started throwing more after 2 BYU TDs. The TOs and 4th down stop were a few good plays (but also helped by Utah State mistakes) that really helped. But we're not going to get those TOs against better offenses, so we need to figure out how not to get pushed around on the defensive LOS, and stay disciplined.
Offensively, you are correct that BYU struggled in the first half--didn't help that they almost never had the ball. But they figured things out in the second.
So I don't have as much concern about the offense as the defense.