Why Darth Vitiate would rebuild quietly before challenging Palpatine

What damage could Darth Vitiate cause if he appeared two years before the Battle of Yavin?

Less immediately than his personal power suggests, because he would arrive without a fleet or political base and would probably rebuild covertly before confronting Palpatine.

The scenario places Darth Vitiate two years before the Battle of Yavin, without the fleets and followers that once supported him. Personal Force power could make him dangerous to Palpatine, but defeating a rival would not automatically deliver control of the Empire. Covert rebuilding is therefore proposed as a more plausible first step than an immediate challenge. The Imperial Security Bureau and Inquisitors would have reasons to investigate a growing rival organisation, potentially drawing Vader into the conflict. Different loyalties to Vader and Palpatine complicate the prospect of simply inheriting their forces. These are predictions about the fictional scenario, with institutions and followers as the key constraints.