It's about the network effect. As it stands now, the network effect is built on the backs of many different nodes on the network all contributing together.

But as you've seen, the amount of people on the network is nothing compared to the total of all the Threads users (~30mil). Once they federate with the rest of the network they will provide a MASSIVE boost to it's enharent value. As people from other instances connect with friends, brands and public figures and alert services on Threads they are slowly becoming dependent on that content.

The users on Threads are not going to be as privacy or technology curious. Almost all of them will be existing Instagram users. They're not going to move to another instance, especially if they can't keep using the threads app, which could have features the other instances don't support.

Almost all social media platforms have this network effect because they were first and/or strategically built their network.

Facebook utilized Universities, requiring uni email address to register and they had features that made it easy to connect with your classmates. Once they hit a critical mass they opened it public.

Twitter piggy backed off of the 2007 SXSWi conference. Displaying pubic Twitter feeds from users at the event on large LCD TVs, they connected users with a similar occupation and intrist. Sending their tweets per day from 20,000 to 60,000.

Threads is building it's network on the back of Instagram while also on the back of Twitters failings. They're co-opting the bad vibes of Elon Musk to syphon users off the platform.

Ultimately, there will be a short term boon in the perceived "value" of the fediverse, and in reality, Threads and Meta will make up a large percentage of that value. Over time, people will have become accustomed to the content Threads provides and when Meta nolonger needs to be federated, people will leave with them.