Pegula does have a questionable track record for hires, I'll give you that. People seem to forget he offered the Sabres GM position initially to LaFontaine, a guy with zero front office experience. Even Patty was dumbfounded and turned him down.
But, we also shouldn't forget that the "St Doug" story probably was true and he was an arrogant ass who made the decision to quit (likely perfectly confident as to gaining another NFL HC job). Again, he's the one who quit, but it's almost certain all is well because he really wasn't going to lead the Bills anywhere and likely would have been fired next season anyhow.