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.
When mastodon got a lot of attention late last year during the twitter exodus I decided to check it out. I wasn't on twitter in any meaningful way, so for me it wasn't a replacement.
I like the ideas behind fedi - I grew up on IRC in the 90s, and fedi feels familiar, like the old internet: distributed, messy, personal... anyways, I ran a one person mastodon instance for awhile, until I realized I wasn't into it enough to warrant the time. So now I just join other people's instances ;)
By the way thanks for setting up the Lemmy instance. @[email protected] when you decide to make uFail stick, please let us know how to support you and the server. Cheers!