I heard about via some friends who are into privacy tools and open source software. I first joined Diaspora and then was introduced to Mastodon, Pixelfed, Misskey, etc.
Long time ago I was reading stuff about distributed systems and I read about ActivityPub. Given all my real-life friends are using corporation-based social networks, I never made an account in Mastodon.
Until a few days ago that I tried to upload a cat video to Instagram and it lagged a lot. It was very frustrating. I noticed how ads were loading super fast, though. So I finally decided to create an account on Mastodon.