Take your pick. It was either incompetence or bias that lead to the investigation against President Trump. Either way, it is a sham and it should have never gotten past first base, if that far.
Those guys ruined several lives and they don’t seem to care. I sort of get the feeling they are proud of themselves. Right now, I doubt that there are many FBI agents that are proud of them. Which reminds me. They also did a pretty good job of sullying the reputation of the FBI for a few decades.