Good question. Right after 911 we needed "area experts" and "language experts". Organizations connected to Muslim Brotherhood were happy to provide the resumes.
So MB infiltrated every agency of the government starting early on.
Then, of course, we elected Obama who is himself surrounded by MB; in my opinion he is MB.
So while before you could say they infiltrated, since 2008 they hold policy positions at the very top.
It is in my view one of the greatest feats of geopolitical judo in history, that 8 years after 911 Muslim Brotherhood occupied the White House.