If (and I say if) Underwood was complicit in what was going on at OSU, do you think that stopped cold turkey when he crossed the Mississippi?
No, neither do I prescribe to the popular belief that all coaches who were ever employed at Illinois all of a sudden became saints during their tenure here.
But Underwood has been at Illinois for a very short time, had to assemble a staff from scratch without previous ties, and currently has no 2018 recruiting commitment. So by timing alone, chances that he already got in trouble (at UI) are extremely low, especially given that he was not named on the federal indictment despite one of his assistants being in close surveillance for some time. Even if the FBI uncovers some improprieties during investigation, chances that it is from his very short time at UI are extremely low, really non-existent.
Now moving forward, even schools and coaches who were regularly cheating, will all of a sudden be extremely careful knowing what just happened. This is not the helpless NCAA, nobody expected the FBI. This is a game-changer IMO.