Roberts is compromised somehow. Someone or some group is controlling him either by threat or by blackmail. His decisions are not Liberal or Conservative. They are absurd, and illegal, and always favor the Democrat Ruling structure. Someone has some very big and very damaging information on Roberts.
Impeaching him would be doing him a favor. It would get him out from under whatever coercion it is that is directing him to rule a certain way, without him having to resign which he is likely forbidden to do. I believe Roberts would love to be impeached.