I'm going to take a different angle for my answer: Content.

There were a lot of people rallying around secularism but they had no guide post. The Intellectual Dark Web and similar groups of grifters targeted this unorganized group heavily with videos, posts, meet and greets, etc. They offered a direction to people who had no direction (in part because their cultures were predicated on members being traditionally religious). They made people feel heard, like they were special.

It shouldn't surprise anyone that a large number of self-identified atheists at the time were being reactionary and hadn't really detached from their religious programming - this was a huge talking point / criticism back in the day. It was true of many even though it was not true of all. When these reactionaries in particular chased after the IDW, it destroyed the fabric of the emerging community. How was a loose-knit, unorganized bunch of atheists supposed to survive half of its members becoming an army for religious cryptozealots?

The Islamophobia was obvious and disgusting. It was a mess of double standards. There was pushback against it - I gave quite a bit myself - but pretty quickly it had become too late to nip in the bud. We all fractured apart and the few existing spaces were absolutely overrun by reactionary ideologues. There was no longer a point to interacting with these groups. Inside of them, atheism was no longer even a common talking point. Instead it was the alt-right's talking points that took over - and standing in my shoes, I have to say that I still believe there was a concerted and inorganic effort to make it that way. But ultimately their efforts worked and that's all that matters.

I was already a Marxist (my atheism was also a big factor in my rejection of western hegemony) but I leaned more heavily into Marxist spaces as we all scattered in the wind away from the brigaded communities. I think I'm probably in the minority in that regard, but I know that I was far from alone.

I think this was a wakeup call for many of us about the continued strength of cultural religiosity and the challenge of actually deprogramming.

My takeaway was that there is serious work needed on the cultural and educational fronts before they can start changing the course of the material front. Or conversely, a massive material state change to provoke cultural adaptations.

However if part of the issue really was a lack of guidance outside predatory and exploitative grifters then I believe it reinforces the idea that more non-reactionary role models and content would help to counter those reinforcing the status quo. If there had been a coherent alternative to the IDW at the time, they may never have taken off.

This opinion is also a bit of self-criticism because I hate clout. I don't want a platform. I despise influencer culture. I think dialectics among communities should guide us, not the half-baked ideas of "Great Men" on youtube. But these preferences are not highly compatible with countering the effects of influencers like the IDW on directionless individuals. My anonymous pushback might have been well-constructed but it didn't move the needle even a single tick. Meanwhile the IDW was offering a pre-packaged and microwave-ready ideology that reinforced deep-seated biases and could be defended with "Just watch **** on youtube" instead of requiring individuals to personally explain their arguments. There was basically no contest.