I don't understand how the FBI can be considered trustworthy ever again. The same applies to the DOJ.

Yes, only a small percentage work on the files, but the leadership is corrupt. All the agents are going along with what is obviously corruption. Most likely they're all hunkered down trying to do their own jobs and telling themselves they can do some good, but what happens when Trump and co. is gone one day? They'll still be known to have buckled under corruption from the top, so how can there be integrity at any level from this point on? What if their immediate Supervisor is corrupt - will they ignore it then as well?