We've gone back and forth on this before, but I genuinely don't understand this argument. Coaches move around all the time. Different positions, different sides of the ball. The outlier is someone who just coaches one position and that's all they ever coach. Like, we think of Scar as the all-time OL Guru, and he certainly coached OL for the bulk of his career. But he's also coached DBs, ST, TEs, been a general defensive assistant, etc. Between college and pros, I think Charlie Weis has coached every single position on the field that there is, both sides of the ball. Thinking a guy who was a really good coach at Position X could also be a really good coach at Position Y isn't arrogant or naive. It's just the nature of coaching.
The biggest problem, as I see it, that Bill ran into was the sheer amount of on-the-job-training coaches he had on offense. Everyone but Caley was new to their role and/or level of responsibility. In a vacuum, some of these coaching choices probably would have been fine. But when essentially every single offensive coach is trying to figure out their role & responsibilities on the fly, that's a pretty big cumulative effect. That to me was his biggest lack of judgement as opposed to any individual move.
