* No bomb explosions seen
* No bomb explosions heard
* No bomb explosions detected on seismic monitors (which should have told you that no bombs were used).
* No evidence of bombs recovered from ground zero.
With no evidence of bombs, you have no case.
That's how to investigate all crimes, First, remove all the evidence of a crime, then conduct the investigation.
See any proof ? None.
So it wasn't a crime, right?