It's been said a few times by people but at the end of the day, Bob did like aspects of Bill's program (Bill personally, draft history, siloed culture, etc he did not). He wanted Bill's organizational structure, but tweaked and modernized.
It took a year or observation, chaos, and failure for Bob to realize he needed a guy like Vrabel.
It's almost similar to the Parcells-> Carroll/Grier-> BB transition. One program to a radically different one to back to something similar.
I don't think BB and Vrabes are similar but philosophy and approach are more aligned than polar opposite.