That was he General that was interviewed by the FBI - who had a recording of a telephonic conservation he had with the Russian Ambassador who phoned him when he was in the Trump takeover team in 2016. That is fairly normal when a takeover team of a new President took over and foreign countries try to find out what is to be expected from the new President. Having had a recording of the telephone conversation they asked Flynn for an interview on the issue and told him he is not going to be under oath and did not need a witness or lawyer to be present.
Strzok was one of the interviewers. After the interview in terms of standard procedure the 2 FBI compiled a report on the talk and found nothing illegal or irregular to charge Flynn with. So Strzok drew up a revision of a report with a very weak implication that the call was illegal and sent it to his girlfriend who worked in the WH. She told him what he drew up was rubbish and set about together with the WH lawyers to falsify the whole record of the discussions and filed it with the FBI.
The report ended up with Mueller who instructed that Flynn be charged with a criminal offense based on a falsified report of what happened. However, before the charge was laid the falsified report was leaked by the WH and a media storm broke out all based on the lies relating to Russian Collusion and Trump withdrew his nomination as head of the CIA. The case dragged on for two years and Flynn had to sell his home to cover legal expenses and got into financial trouble. The FBI then went to him and said they have evidence of some illegal work his son did and unless he admitted guilt to his charges they were going to charge his son with some charges. It all was a lie - the FBI had nothing against his son.
Flynn then on the advice of his lawyer pleaded guilty to the charges laid against him. However, he got a new lawyer and she asked the FBI documents related to the case. The FBI initially refused to make the documents available and she took the matter to Court forcing them to provide the documents. Barr also called for Flynn's file and found out that there was evidence of criminal lawbreaking conspiracy by Strzok and his WH girlfriend on file and instructed that the case against Flynn be withdrawn. The Judge hearing the case refused to accept withdrawal of he charges - but in a regional court hearing the case was thrown out of court by a full panel of judges.
I think Flynn claim damages from the FBI and the matter was settled out of court. Bar should have charged the FBI officials involved with criminal conspiracy to create a crime which did not exist and sent the two bastards to jail - but by then Comey and Strzok were already fired by Trump and he did not take further action against them. Flynn claimed damages from the FBI and the matter was settled in his favor.
I studied the documents involved - it was made available on the internet and to my mind it was real proof that the FBI became an arm of the Democrats used by them to get at opponents.