And he knows an investigation is under way and that he can't put his thumb on the scale
Since he picks 'em, he sure as hell knows what it not only takes to secure a warrant but also what is needed to reapprove them 2-3 more times as evidence must support to do so.
Something(s) you clearly didn't know.
Roberts picks FISA judges. He has a vested interest to ensure those courts aren’t bullshitted into fake warrants.