I think your mistake is in trusting a partisan GOP memo as presenting the entirety of the relevant facts. That's like taking a Liberal or Labor (or Greens) press release and treating it the same way as a legal judgement.
The memo says that information from the Steele dossier formed an "essential part" of the 2016 FISA court application. It makes no attempt to back that statement up with evidence so it's simply a bare assertion from a partisan political source.
A GOP memo could say the sky is red, but unless it can back it up you wouldn't believe it would you? Or would you?
