They were killing each other long before Western nations became involved which was about the time the Ottoman Empire fell due to the fact that they backed the wrong side during WW1.
Not really just because of that, the Ottoman empire fell from within first because Arabs got sick of being frozen in time for over 500 years, while the Turks were improving their homeland in every way possible on the Arab's expense. And hence why Turkey is so much ahead Arabic countries even today.
The French and the British promised the Arabs a united Arab state if they fight the Ottomans. So the Arabs did, but were rewarded with western occupation instead of liberation. Guess who backstabbed the Arabs/Muslims then proceeded to support dictators in almost every state? You got it, the good ole freedom promising West. Aaaah now the the picture just got a bit clearer didn't it?
Who still supports and finances dictators across the Middle-East the Muslims or the West?
Husni Mubarak has been the president of Egypt for 40 years and is soon to handoff the presidency to his son for another 40 years. Who supports him against the will of the Egyptian people? You got it we do. Who supports the house of Saud? We did.
Who planted Israel in the middle of Palestine? The Brits did. Who has financed Israel since it's inception and allowed it to gobble up Arab land and kill Arab civilians? We did.
Yet all the blame ends up on the Muslims somehow because they can't find a way to move forward so they turn to extremism?
When do people turn to extremism? When life is comfortable and freedom is all over the place? Or when they are kept in poverty and their rights violated constantly?