Some. They hate Trump, and they don't care that the nationalysecurity apparatus was used against a political opponent. But there are probably others who are just clueless. They believe Brennan's lies about Trump "collusion" or have doubts about it. So they hop on board.
The important point is while they still have their clearance, they normally have no access to any relevant classified information. They will not know, for example, about the redacted info in the FISA warrant. Even if they are acrtively using their clearance on a program, they will only be reading classified stuff relevant to that program.
Either way, whether deep staters who know the real deal, or just idiots, it's impossible for us to know the difference, They all need to be stripped.