There's a vast difference between an every-down expensive player who likes to freelance and screw up plays (which is what he was) and a probably relatively cheap spot player who can be put in the game in situations where his freelancing might actually be useful (which is what he'll probably be). Belichick will put the hopefully humbled, talented, and still relatively young player in situations where he can succeed and help the team at the same time.
And, if not, I'm sure they're paying little enough that they will buy him a bus ticket to Logan at any moment. Hell, he may not even make it through camp if he doesn't show he's a smarter player.
I liked cutting him then. I like signing him now.