My guess is that they audited his communications and found some smoking gun already.
I also find it interesting that Baseball has gotten so far out so far in front of this story, over a month before its reolution. Seems to me that were Clase a relatively isolated incident, they would go through the investigation of him on background and out of public view. Instead, the situation is not even resolved and already we know. That probably means either the Clase situation is already very well known and liable to come out through some other source, or that the gambling rot among players is so deep that Baseball is trying to get control of the situation before it completely blows up in their faces and jeopardizes their billions in gambling partnership money.