I've read the memoirs of a Mossad agent who later became the head of operations and he noted about the "romantic" period in global Terrorism. heavily paraphrased: "I remember when they (terrorists) used to recruit in the ivory towers of the universities of Beirut, Damascus, Baghdad, and Tehran. Using the words of Marx and Lenin rather than those of the mufti."
He later goes on and discuses how drastically different they were even tho they would be just as ruthless you could talk to them when needed, and if not at least respected them for having a philosophic ideology rather than blind faith.
He also added some anecdotal evidence on that matter. "When we needed to find one, we knew not to look for them at the mosque or at the madrassah, but rather at a titty bar in east berlin. As one would be much more likely to find one ("terrorist") snorting cocaine of a stripper than listening to a sermon or hunching over hadits in a dim lit room".
When talking about how they compare to the Afghani mujaheddin he made another anecdote saying that the average Arab terrorist at his time would be wearing blue jeans and a bright polo and walk around with a ringo star haircut rather than have a beard and wear tribal rags.
Religious [Islamic] Terrorism / Militarism picked up steam in the 80's and onwards and you can literally distill it to 3 major (and somewhat interconnected) events.
1) The Islamic Revolution in Iran, heavily religious, very devout, used religion as a primary source of power and more important for divine mandate. This lead to the formation of Shia groups around the globe like Hezbollah which put allot of Sunni's in panic mode as they would be just as likely to fight against them as they would against "Zionists" and "imperialists"
2) (heavily interconnected with 1) The soviet invasion of Afghanistan, this is what gave the Sunni the break they needed. Anyone who've been, or read about the history of Afghanistan or Pakistan knows just how "nonreligious" they were this doesn't say that they weren't Muslim, but many especially in the tribal and nomadic regions weren't the example of a devout Muslim one would think of today. They didn't had mosques (some of the bigger villages had a house of prayer, but not a mosque as it's a bit hard to build a minaret from mud and straw) many of them haven't seen a Quran in their life and the few that did couldn't read Pashtu, Urdu, or which ever language they spoke out of the regional 5000 languages yet alone Arabic.
But none the less the Salafist seized the opportunity because they were one of the few that could (and they desperately needed it), you can't really fight Soviet communism with Arab communism/socialism, Iran wasn't in a position to do anything about it (nor did it want too) so a fight against tribesmen was turned into a fight against holy warriors due to the lofty assistance of Salafists extremists mainly from Saudi-Arabia and the minor gulf states.
This later turn to sprout the Global Islamic Jihad and it's various local chapters like the Palestinian Islamic Jihad, it was the 1st time in nearly 40 years that west had to deal with religious ideological Islamic terrorism and not the usual socialist/communist club.
3) The r decriminalization of the Muslim Brotherhood and the release of it's leaders form Egyptian jails following the assassination of Sadat, this lead to spread of more religious ideology and lead to the formation of groups like Hamas in Gaza and Harakat Al-Islah in Somalia.
So sorry people will always find reasons to kill each other, with a few flaps of the butterfly wing we could've been still fighting socialist Arab/Near Eastern terrorism rather than Islamic one and it would be just the same just under a different banner.
[0] https://en.wikipedia.org/wiki/Popular_Front_for_the_Liberati... https://en.wikipedia.org/wiki/Ba%27ath_Party
