I don't recall Russell being very prolific in college passing. In fact, I always thought he sucked.
3100 yards his final season, 28 TDs and 8 INTs. QB rating 167.
2400 yards, 15 TD and 9 INT with a QB rating of 136 the season before.
Cam Newton went for 2850 yards, 30 TDs and 7 INTs. QB rating 182.
Pretty similar passing stats. Russell had a few fewer sacks but he wasn't a running QB like Newton.
I never understood how anyone thought Russell was a 1st round pick, let alone #1 overall. He was an average talent with no brain. Leaf, on the other hand, did a great job in college and him being a bust was just bad luck for the Chargers and was due to his attitude more than anything else.