You’re complaining about ads that are being pushed on you by an algorithm from ad companies. I’m telling you there are no ad companies. Seems relevant.

I never typed the word "ad". I specifically said post of top brands. How can this be achieved in ActivityPub? Easy. When you are using lets say Threads, their proprietary system treats differently ads and normal posts. However, anything their system is pushing on the federated network (ActivityPub) is disguised as a normal post. A post that is having millions of engagement will be visible in "All".

Nothing prevents them from doing that right now.

You act like you're new to internet. What prevents them is that their audience is not here and companies are not paying them for that. However companies will pay them to promote their products in Threads. With the current numbers, Threads has the potential to dominate the "All" page.