It was allowed to happen to provide an excuse to start those wars. There was a very high level general in the israeli military who had the plan to invade and destroy 7 countries, and since 9/11, America has gone to war against 6 of those countries and their government leaders have been removed and replaced.
Guess which of those 7 countries was not destroyed in a war yet? Iran, and you see how hard they work now to try to promote a war against Iran.