When Devin Nunes stepped away from the Russia probe despite his position as the Chair of the House Intelligence Committee, it was a major victory for those seeking to obfuscate and stall one of the two tracks of investigation: The unmasking of names that Susan Rice has admitted doing, though she claims no political motive.
The event precipitating Nunes withdrawal was a series of ethics complaints filed by left-wing groups, including MoveOn.org, which triggered a House Ethics Committee investigation. That fact that there is an investigation means nothing in itself.
Mercedes Schlapp points out how the tactics used against Nunes helped shape the ultimate decision: