Honestly, one of the bigger factors was money. Lynn Swann is an incompetent AD, and extended Helton's contract. If they
fired him last year, they'd have to pay $15M + to buy him out. (That's a lot of money, but not that much for USC.) It's bizarre.
His hiring was also bizarre. Sark got fired in October 2015, and Helton became interim coach. (USC was 3-2 at the point Sark was fired.) He went 5-2, as interim, and was made permanent HC after beating UCLA... And then they lost the CCG to Stanford, and the Holiday Bowl to Wisconsin. The next year was weirder- they start out 1-3 (Losses to Alabama, Stanford, and Utah. Only win- Utah State.) But then they win out, and beat Penn State at the Rose Bowl.
Horribly inconsistent.
I think Helton would be good at other schools. But not USC. And Swann had NO business taking the AD job. Both need to be fired.