It is the Factory of Sadness for a reason. Having said that much, you're right, BB did quite a lot more than he gets credit for during his time in Cleveland. But my point was simply that your first job isn't always the best indicator of what you will become. He definitely learned a lot of things during that first stint in Cleveland, things he would later apply as head coach of the Patriots.
He pushed hard to sign headcase Andre Rison to a record-setting deal, then cutting him one season later. His benching of Bernie Kosar was the correct thing to do, but the way it was handled disrupted the locker room, and I think it shaped how he dealt with the Brady/Bledsoe transition. He also didn't delegate much while with Cleveland, one of the biggest changes according to people who worked with him during the Browns days.
If BB hadn't grown from the Cleveland job, if he hadn't adapted and learned, no way he's as successful as he has become. He continues to learn, adapt, and get better.