Groups like ISIS don't last more than a few years. The group starts out with a bunch of hardcore fanatics who truly believe in everything they preach. Then a second wave of recruits come along who still believe what the first group believes in, but maybe not quite as much. Then you get a third and fourth wave of recruits who happen to be lonely and depressed, saw ISIS on tv and thought it would be awesome. They're less about the fanatical beliefs more about wearing those cool looking black outfits, getting to show off with a big gun, raping as many women as they want and getting paid for all of that. They see themselves as rockstars who will cut off someone's head for listening to rock music. These wannabe rockstars will often put up less of a fight, be more willing to surrender and will try to get out of fighting altogether.
Al Queda on the other hand is still lingering around mostly because the very people who are supposed to be hunting them down keep giving them money and weapons so they can kill other terrorists. Go figure.
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