I personally dont think the weather has to do with it. The fact that Southern Cal gets the nations top recruits (until recently) is probably the main reason. They always have a killer O-line, making the job easier. Almost always have a RB that will play pro, along with some WR's. Those things might make a qb look better than he really is.
I always liked Sanchez.. which is saying a lot because USC is at the Cowboys level of hatred for me. I wish Carson Palmer had never hurt his knee, his career looked so promising until then. Leinert is just a
He may have been a product of my first paragraph. When you have to stop Reggie Bush and Lendale White, Leinert's job is much easier.