Strzok is known for his extramarital affair with former bureau lawyer Lisa Page. The pair exchanged tens of thousands of texts, many of them anti-Trump. Some of the most infamous texts were the ones where Strzok and Page discussed an "insurance policy" concerning Trump, with the former outright saying that they would stop a Trump presidency, whatever that meant. The two also worried that the FBI was going too hard on Hillary when the bureau was investigating whether the former first lady had mishandled classified information while serving as secretary of state via her unsecured and unauthorized homebrew server; Clinton conducted all official business through this server.
Now, Mueller’s investigators, most of them partisan Democrats, are a bit irritated that Attorney General William Barr’s summary didn’t really touch upon the severity of their findings...allegedly (via NYT):