Because they have a rep for this. Ask Schumer. Undoubtedly, Obama's advisors -

have warned him. The continuous leaks from "unnamed intelligence sources" that almost every MSM news outlet have been using over the past year should tell you that the IC has a problem. Trump also has been very pissed off about there screw up on the WMD intel - even after all of these years. It is hard to explain how they could get that one so wrong. It cost W a lot when any president would have believed it.