These weren't "normal" firings or demotions. All came from the OIG investigation you haven't been paying attention to.
"Deputy Attorney General Rod Rosenstein told Congress that he expected the IG report about that era to be complete soon, although it is not yet public. There have been indications that early drafts have circulated internally with some consequences already: Former Deputy FBI Director Andrew McCabe, who had been expected to retire this year, may have done so because bureau officials were anxious about how the Horowitz report treated his role in the Clinton email matter or other cases.
https://www.npr.org/2018/02/28/58948...e-appears-thin
Bruce Ohr had previously served in the deputy attorney general's office, but according to a source familiar with the situation, was demoted amid the discovery of certain meetings with Fusion GPS founder Glenn Simpson and Christopher Steele, the former British intelligence officer who assembled the dossier.
https://www.cnn.com/2017/12/15/polit...ohr/index.html
The trap is set man.
Special counsel Robert Mueller removed one of the FBI's top Russian counterintelligence experts from his team of investigators after an internal investigation found messages he sent that could be interpreted as showing political bias for Hillary Clinton and against President Donald Trump, according to US officials briefed on the matter.
https://www.cnn.com/2017/12/02/polit...ion/index.html