He has nothing to lose but his life. He keeps mum, maybe he’ll get out of prison. He talks, maybe he won’t.
If he gets out of prison, he will still, most likely, lose his life so he can never talk. Either way he is doomed. Whether he wants to get back at the people who allowed him to be prosecuted is another question.
OR...he needs to spill his guts before he can be silenced. Coin toss?