I’ve thought about this as I was someone who jumped onto Mastodon as soon as Twitter went dark side. I think the reason it never became a go-to for me like Lemmy has, is the fundamental difference in how I used Reddit and Twitter.

With Reddit, while I curated my feed by following subs, I was really looking for something to cover me when I was idle for a time, and wanted to scroll. I am not too choosy about what I want to see, just surprise me.

Twitter was strictly a service that I used to follow organizations and individuals. I never went to trending or anything like that. My follows were just accounts I gained interest in somewhere else. Mastodon failed because probably less than 10% of the accounts I followed even tried the service. There was nothing to see.