I think it might be possible that the backround check turned up questionable thing, perhaps things this Mr. Faisil didn't even know he did. For example, JB's extensive background check may have turned up evidence that Faisil donated money (perhaps unwhittingly) to a Muslim charity known to funnel the money to terror operations. Or perhaps that he actively attended a Mosque where (perhaps out of his view) pro-terrorism stuff was preached/discussed/planned. Those are just what I think could be general examples of the kind of stuff that may have caused JB to rescind the offer. But as they say, it'll all come out in the wash.