As much as I hate to be that guy, it's worth keeping in mind that BlueSky is not really practising what they preach here. The AT protocol formally allows for a kind of decentralization, but it is prohibitively expensive to run an instance, meaning that only rich folks or those who are willing to accept money from venture capitalists will be capable of actually doing so.
ActivityPub already existed when they started BlueSky. They chose to not make their protocol compatible. The reason is simple: They are a company, and they have a profit motive. ActivityPub is too democratic, and therefore hard to monetize. By now they have a bunch of crypto bro investors who want their money back. It's better to leave your money elsewhere.