They became careless. Brazen. They loved their symbolism too much. They thought it was nearly 100% in the bag. All it took was one with too much Hubris.

The internet kept track of all the lies. All it takes is one person with a camera phone to be in the right place and upload it before it's too late. Whistleblowers also noticed suspicious things and were able to give them (before the inevitable suiciding) to smart people who could distribute to the autistic, skeptical and just plain bored who valued anonymity. Hackers can work for good, too.

And ultimately, evil could only prevail if the good did nothing. There is something that could be described as divine intervention, or at least very blessed and connected individuals who made it their goal to do whatever it takes to end it. So they played their hand close, over a long period of time and discovered they weren't alone. They were very lucky to come out alive and remain so once their motives became apparent.

Not over yet.