I think you're making a lot of assumptions here, many of which I have contentions with.
we had very little moderation in the early days of the internet and social media
It differed from site to site, but in my experience of the Internet in the '90s and '00s, a lot of forums were heavily moderated, and even Facebook was kept pretty clean when I got on it in ~2006/2007.
and yet people didn’t believe the nonsense they saw online,
I fully dispute this. People have always believed hearsay. They're just exposed to more of it through the web instead of it coming verbally from your family, friends, and coworkers.
unlike nowadays were even official news platforms have reported on outright bullshit being made up on social media.
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We live in a world of 24-hour news cycles and sensationalization, which has escalated over the past few decades. This often encourages ratings over quality.
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Mainstream media has always had problems with fact-check. I'm not trying to attack the news media or anything, I think most reporters do their best and strive to be factual, but they sometimes make mistakes. I can't remember the name of it, but I there's some sort of phenomenon where if you watch a news broadcast, and they talk about a subject you have expertise in, you're likely to find inaccuracies in it, and be more skeptical of the rest of the broadcast.
To me the problem is the godamn algorithm that pushes people into bubbles that reinforce their correct or incorrect views
Polarization is not limited to social media. The news media has become more and more tribal over time. Company that sell products and services have been more likely to present a political world-view.
Overall, I think you're ignoring a lot of other things that have changed over the years. It's not like the only thing that has changed in the world is the algorithmic feed. We are perpetually online now and that's where most people get their news, so it's only natural that would also be their source of disinformation. I think algorithmic feeds that push people into their bubbles is a response to this polarization, not the source of it.