The bombers are useful idiots. True believers that aren't aware that they're part of an inside job.

Right. You just fine someone else that wants it done and grease the wheels.

That's what you need true believers for: cannon fodder. Unlikely for someone to chicken out if they're already heavily emotionally invested in the idea of achieving spontaneous unity with God by blowing themselves to bits.

> The sticking point would be the bombers themselves. Maybe they chicken out at the last minute and then expose the conspirators.

Very trivial to deal with, if one of them starts to speak up you just send the FBI to conduct an "interview" during the course of which they can be assassinated, like they did with Ibragim Todashev.