Their QB throwing INTs is not good luck for BYU. It is a bad play by their QB caused in part by BYU's good play.
Our punter returner trying to field a punt over his shoulder and out of reach is not luck. It is a mistake and a bad play on his part.
But as another poster said - the ball could have bounced 10 different ways or more. The fact that it bounced up so perfectly into his hands that he didn't even need to break stride and so that he could continue sprinting across the field is complete luck.
After the lucky bounce he makes a great play. But without the lucky bounce then the return never happens.
Not sure why this is hard to understand.
And whether BYU would have scored on the drive has nothing to do with whether it was a lucky bounce or not