Such warnings crop up on intelligence reports continuously and most turn out to be in error. It is very difficult to determine, when hearing a thousand little bells ringing, which is the one that signals something important. It gets much easier after the fact to point at the right bell, as you Michael Moore and Donald Trump are doing.
Yes...It’s hard to keep the country safe in the climate but that’s the point. He wasn’t able to (even if he tried). One can certainly argue that someone who had that as their absolute main focus could have shook the right tree