Comment by mal-2

The federation occurred when the post was made, it was sent out to other servers and stored there. Then it got served to those users directly, without further contacting chaos.social.

To understand how it's decentralized, search for @jonty@chaos.social on your own fediverse home server and the post will pop up.

There's a particular user story here which is a bunch of people who don't have accounts on any server, wanting to see the content from a central location (chaos.social). I do think it's worth talking about this story and ways to fix it but it's not really accurate to blame it on the federation behavior.