We'll set aside whether Grobe was actually truly offered the job over current head coach Bo Pelini -- Grobe probably would have had to accept some of the assistants that then-AD Tom Osborne strongly suggested to Pelini -- but let me tell you how I read that answer.
Grobe regrets not leaving Wake Forest, which clearly peaked in 2006, 2007 and 2008, and he regrets not sticking to what made Wake Forest a decent program in the first place. He thought the administration would build him facilities to compete. Apparently, they're not good enough. He drifted away from his misdirection run offense to a pro-style attack. With success, he started getting into the living rooms of better recruits, which meant more talent, and, in his case, meant more headaches.
What's really interesting about this Grobe story isn't some wistful notion that Nebraska would have been better for him. It's that Grobe got away from his principles for building his program, administrations couldn't deliver the all the facilities he wanted, and Wake Forest got worse.