He must be hiding some nasty stuff.
My though, he asked for a way out, and his role, me thinks, is to make sure that evidence goes public. This impeachment was not going to allow it, since DS controls the rules, but by ensuring that acquittal happens, he can push for a civil case that will allow for discovery to happen.
If he convinces us that he is against POTUS DJT, he will definitely convince the DS.