He should have had more time. They never moved this quickly, not for him, not for anyone. It must have been blackmail, somehow, or direct intervention of Eru, or some corruption in the ring clouding his thoughts...or any of a thousand other possibilities that are no longer useful for him to consider.
He stands before the court and speaks and begs and weeps. He still has the ring, at least. He prefers not to pull the same trick twice, but it wasn't him who played it last time, so he draws on his power and twists his words in their ears to sound like oaths of repentance.
It doesn't work. They declare that he has gone beyond his station, grown stronger than he has right to be. He no longer fits within the intended story, and must be cast out so he does not corrupt it further. He should have hoped the elves would hear that he committed his only true crime in being helpful to them, but he can't quite bring himself to care. He struggles against his bonds, he twists his shape and burns his jailors, but in their direct presence even his newly forged power is all but helpless.
He is to be cast past the edges of the world, displaced from all space and time so he may sully their creations no more. It feels something like falling and it feels something like sleeping, and then all of a sudden, it feels very much like hitting the ground.