Conspiracy theories have always existed and the jury is out whether they are more prevalent now than in the past. See https://knowablemagazine.org/article/mind/2021/the-enduring-...

But I see social media as a place where people feel permitted to share conspiracy theories. If you engage with social media a lot it seems half the world is crazy. If you only engage with people in real life people are seemingly as sensible as ever, because social conventions force them to mostly keep a lid on things.