I think of PESETAS as more defensive than what a single protocol can handle. Imagine posting to Bluesky and using automation to syndicate the post to Twitter, Facebook, Mastodon, Threads, and more. If Bluesky goes evil, or you otherwise decide to ditch it, you've mitigated the network effect as you have followers on other platforms already. People can still find you and your content isn't lost.

Imagine if Bluesky decides to ban you, and continues to ban accounts you create elsewhere. Atproto ensures non-Bluesky PDS can see you, but you've lost 99% of the userbase.