Honestly, where is the cold hard proof that he allowed it to happen?

Still, it is a rather pathetic tactic America has used throughout history, provoking people so it isn't them who starts it...Fort Sumter, the Rio Grande, what some people think happened with the ship that started the Spanish-American War (though there is also a good chance that either it was sabotaged or its the fault of the cargo that spontaneously combusted ).