Twitter copied all of those features from other apps. Spaces = Clubhouse, Fleets (which was also cancelled last year) = Snapchat. At best, Kayvon was good a being reactionary to competition. Not that great of a track record.
Fleets as in fleeting. I thought it meant “group of ships” and seriously struggled to see how the name connected. Mind you, my use of Twitter is confined to “order by time desc” and Lists.