I suppose the better word would be it never “caught” a single planned act. Your point can be taken that it is impossible to prove whether or not it stopped an attack due to deterrence effect of awareness of the surveillance. Though I would argue that it would have simply made them more guarded and difficult to monitor (using E2E encryption, etc), and so the effect is that only carefree generally lawful folks actually got caught up in the surveillance.
It stopped attacks from entering the planning stage and made the “job” of terrorists harder.
It did not. Look up the story about thinthread. More information is not more useful. Radicals generally resent rather than obey the panopticon.
I suppose the better word would be it never “caught” a single planned act. Your point can be taken that it is impossible to prove whether or not it stopped an attack due to deterrence effect of awareness of the surveillance. Though I would argue that it would have simply made them more guarded and difficult to monitor (using E2E encryption, etc), and so the effect is that only carefree generally lawful folks actually got caught up in the surveillance.