The big thing with Trestman and I'm not sure if it was his, Emerys, McCaskeys, or a collective idea, was just trying to squeeze every ounce out of that D (with a coach who never ran the system) rather than a clean break. Clean break that D and bring in young players buying into a fresh system with a DC who actually knew it and maybe that side of the ball isn't as bad.
Trestman weirdness still has a shelf life, but I also recall a bunch of things fans/media freaked out about at the time that actually have been somewhat commonplace by other coaches since then (I.e. Rotating captains). At least some of his weirdness was different, but ultimately fine.