Before the whole Reddit migration I was passively aware of the Fediverse, I thought I somewhat grasped the concept, and had created a Mastodon account, but never really used it.
But once the migration started, I decided to try out Kbin, and really liked it, and even started to use Mastodon more often.
I had heard of Mastodon after the Twitter debacle, but never checked it up more than that (I merely knew that it was a FOSS twitter alternative). So basically I knew nothing about the Fediverse before joining lemmy during the Reddit protest