/r/196 was a popular sub on Reddit, about 500k subscribers. A lot of them were dedicated users who were very active and had recognizable usernames.
196 was one of the first major subs to shut down and point everyone to the fediverse. It helps that 196 was very LGBTQ-friendly and Blahaj.zone is also very explicitly LGBTQ-friendly, so it was a good match.
196 creates a lot of content because their "rule" was anytime you visited the sub you had to leave an image, whether it was a repost or not. This also works very well for a nascent fediverse where not a lot of OC is being made yet.
Thus 196 was pretty much in the perfect position to become one of the biggest places on the fediverse.