Except they have won, they've been winning since Sept 11, 2001.
Every time there's an attack, conservatives overact and we lose more of the freedom we used to have. There's an entire group of people who are scared to leave their house because they think they'll be killed in an attack.
They're the people who vote for people like May or Trump. We've seen it play out time, and time again. An attack happens, conservative politician spews some crap, says it's to try to prevent another attack, and they get rewarded with votes.
Meanwhile, the terrorist groups sit back and laugh their asses off at the result of them getting exactly what they want. Killing people isn't their main goal. Their main goal is to keep the western nations in a constant state of fear, as it's easier to control them. This also allows them to keep manipulating western leaders into keeping the War on Terror going, thus making it easier for them to gain more supporters, cause more attacks and keep the whole fucking cycle going.