I know that Bluesky had a core user base that kept the site alive and it became the go-to alternative when there were big changes made to Xitter such as when it was temporarily banned in Brazil. It also benefited from being the default social media alternative not owned by billionaires which is why many chose it over threads. Many people value moderation and being able to quickly subscribe to block lists made curation easy from the beginning. It created a bunch of silos which people had control over. Mastodon’s interface of different timelines was way clunkier than curated block lists and feeds. People don’t even know about Nostr so you have to get into cultural conversation somehow.