In short: His goose was already cooked, he did so much brazenly stupid stuff in full view of the public and ran his mouth off after doing it that the case looke

In short: His goose was already cooked, he did so much brazenly stupid stuff in full view of the public and ran his mouth off after doing it that the case looked like a slam dunk. If he went on the stand he at least had a chance of convincing the jury that he was unaware that everyone around him was committing fraud. He didn't have much to lose.