While it would probably be difficult to prove (or not, AB is about as dumb as a broken toaster...) I suspect that Brown was ALWAYS trying to get to the P*ts for that ring. The P*ts in fact offered a good pick for him, but the Steelers refused to deal him to NE. Thus Brown had to figure out how to tank whatever trade ended up happening in order to get himself released outright.
Unfortunately, it's hard to underestimate how dumb the Raiders can be, so they ponied up the money and the Steelers made what LOOKED like a terrible terrible trade on their part. Suddenly. Brown is a f'n Raider... with Carr? Ah hell no. So - he begins a campaign of ***-hattery that makes Terrel Owens look like a team captain. He ultimately manages to get himself released from the Raiders without ever even gone through a single "live" practice. He didn't ONCE practice full speed in pads.
Suddenly, he finds himself exactly where he always wanted to be. Released and free. And he signs with the Cheats within a couple HOURS! (Sure... that deal wasn't pre-inked and agreed on. You betcha...) And all seems perfect in AB's world. Except that a couple women start bringing up sexual misconduct issues and his failure to disclose ALL his dirty laundry to the P*ts explodes in his face. And in honesty, if Kraft hadn't been caught in a thai parlor in the off-season the P*ts wouldn't be nearly as sensitive to the whole sexual misconduct issue. But given the fact that Kraft and company don't want ANYONE thinking about Kraft's dalliance, they immediately cut ties in a PR face-saving move.
And now... AB is all alone. Angry that the Raiders won't give him his guaranteed money, angry that the P*ts cut him loose without even letting his case be fully investigated, angry that business is now bustin'...