It works extremely well - it guarantees you know* someone on the social network. No empty feeds, no literally-no-one to talk at, you have someone you can ask questions about the site, etc.
Speaking from experience working on a social site with loads of signup flow experiments: the results are consistently wild. It's no competition on all the normally-valued metrics like interactions and retention.
*for some degree of "know" anyway. Better in most cases than "the news talked about this tweeter thing"
(edit: I do think they may have missed what might be the biggest boat sailing party, which was probably a mistake. But invite-only is quite reasonable.)
It guarantees you know one person on the network. And if you like it and want to invite everyone else – tough luck.
Threads solved the cold start problem by not having a personal feed at all at launch. There is only a single algorithmically curated one, prioritizing first/second/third/etc degree connections and otherwise showing content from everyone else. So the place always felt alive from day 1.
Unfortunately, they likely used AI to sock puppet and prime that pump, along with simply already having a user base.
Nothing very special about those shortcuts. Had they had a standalone system, it's not be much better than all the other attempts. This is akin to how Snoy launched the playstation.
Speaking from experience working on a social site with loads of signup flow experiments: the results are consistently wild. It's no competition on all the normally-valued metrics like interactions and retention.
*for some degree of "know" anyway. Better in most cases than "the news talked about this tweeter thing"
(edit: I do think they may have missed what might be the biggest boat sailing party, which was probably a mistake. But invite-only is quite reasonable.)