I also think Brian just didn't have the experience needed to be able to conceive potential changes. All he had was a couple of years as TE coach with the Patriots, then the time he had under Greg Davis. I think he's probably a smart guy, and the hope was that he could rise to the challenge, but he just didn't have the breadth of experience to be able to do so.
Contrast that to Tim Lester, who came with a notebook full of hundreds of pages of offensive plays, experience running offenses at multiple schools, and a sabbatical with the Packers. The contrast in experience is staggering.