Muslim Electronics Ban

Now Trump is banning electronics from select Muslim countries (as if Muslim travelers themselves weren't enough).  Two questions:

1.  If the threat of explosive devices in laptops is so great, why aren't they being banned on all incoming flights?

2.  Aren't x-ray detectors in airports worldwide supposed to be able to detect explosives?

Or is Trump really attempting to benefit U.S. airlines (whose flights aren't affected by the ban) by driving customers away from foreign carriers?