Classic bootstrapping, using related but unverified accusations to bolster each other. X must be true because A said Y about B, and then C said X about B, after which A repeated C's statement about B, and C repeated A's statement about B. Why would they do that if it weren't true? This is what is meant by creating a myth out of whole cloth.

The key, as with any shell game, is razzle dazzle. We reported on the unverified accusations because Comey presented them to Trump, but Comey wouldn't have done that unless there was something to them, and look everyone else is reporting on it. Would everyone be doing that if there weren't something to it?

Logicians call this "petitio principii" (begging the question, circular argument), but in the end it's just a lot of "oooh look, something shiny!" for the chattering classes to chatter about.