Man, the answer to this is depressing, long, and honestly just gonna piss me off. but I'll give a short answer.

Back in the 90's the atheist and skeptic movements began to take off, slowly on message boards, alt.religion, alt.atheism and alt.skepticism newsgroups. The community was small, tight, and fought like family. When I came back from Alaska after an adventure, there were meet ups and conferences. By the later 2000's the "Four Horsemen" were writing books giving speeches and raising hell. In all but the most backward parts of the US and Canada, saying that you don't believe in god was met with a "meh" instead of violence. I've had conversations with people who had windows smashed, bullets fired through the walls of their homes etc and this was a HUGE shift.

Then, atheism got popular. This kills a movement, sadly. The hanger's on and profiteers jumped all over the movement and guys like de Botton were starting to look at the atheism and skeptic communities as a new, secular faith. They were trying to turn atheism into a church. A sizeable group of the influx were real Marxist/Communist types, and they did nothing but stir shit with the Libertarians and rally didn't care about reducing the roles of religion in our schools and governments. TAM7, the one I went to had over 2000 people! The one in 2015 I don't think hit 1000, which is sad as Randi is one of the great good people out there.

He himself is not the full blame, but the people like him that jumped onto the train as it was gaining steam ended up derailing the momentum. Fortunately it is very hard to kill and idea, and there is still an active atheist community in the West.