Social media provides an ideal platform for creating highly specialized and self-selected subcultures. When the quilters, cat fanciers, antique car buffs, etc. link up, it doesn’t much matter. When the mentally ill do so, it gets toxic fast. They mark their territory and get very hostile when normies show up.
One of the keys is how much time people spend online. There are a lot of people out there who are spending virtually all their waking, non-work hours glued to a screen. And some of them work on a screen as well. Some of them are offended that reality doesn’t conform to the synthetic, wish-fulfillment fantasy they have constructed online.
The internet/social media provides countless echo chambers for those seeking reinforcement and the avoidance of opposing opinions.
It also provides access to the truth, but, as Colonel Nathan Jessup said, most people can't handle the truth.