https://thefederalist.com/2020/09/25/get-trump-fbi-whistleblower-on-mueller-team-details-real-reason-flynn-was-targeted/

The broader Trump investigation was “opaque,” the case theory was “supposition on supposition,” the Flynn probe in particular was “unclear and disorganized,” and its predicate was “not great,” Barnett told investigators. According to the interview notes, he felt there was “little detail concerning specific evidence of criminal events.”