Why did the USSR think that the events surrounding Nixon and Watergate were a coup?

by SpacePirateRolf
orangeResolution

/u/DeSoulis covered part of your question in this answer about the Soviet perception of Watergate.

The Soviet political culture, with its weak institutional and legal checks on executive power, meant that its leadership had trouble coming to grasps with the idea that the president could be forced to resign over abuses of power in violation of the law.