The IG report didn't come close to debunking the idea the FBI was politically biased...
[thefederalist.com]debunking-the-idea-the-fbi-was-politically-biased/
FISA abuse was cited as a concern when that system was created. It's not surprising that there was an incident using it as a cudgel against whomever they didn't like. It just happened to be Trump. Had anyone else gotten the nomination in '16, it would have been used against them too. This was simply an eventuality.