Related Question: I have also heard it said that it is a result of the British and Israel deliberately going much lighter on Islamists than secular opposition. How true are those claims?

I won't comment on the Six Day war but no, political islam was always in the background. It did not just "Suddenly" appear out from nowhere because a nationalist movement failed. The main political opponents of the Baath in Syria as early as the 60's were the MB, the main opponents of the Baath today are another group of Islamists. Either way, it's hard to talk of "one brand" of AN since the MENA is pretty much radically different in situations from one part to another. It makes much sense of taking case for case situations and trying to understand it this way and see how it relates to the bigger picture you're trying to understand. You won't understand the society of Saudi Arabia the same way you would for Lebanon, totally different contexts. Saudi was never AN as a state. Lebanon always had several loyalities depending of the sectarian identity of the person. I think you understand my point.