But really, it's that Twitter shifted hard-right to literal Nazism, and so people left. Which is completely understandable.
At no point did I make this claim. Bluesky's user base self selected for left wing viewpoints because Twitter had taken a hard right turn and Bluesky, mostly by way of moderation, was unwelcoming to the right wing. So left leaning people had a reason to leave Twitter and a friendly platform. Right wing people had no reason to leave Twitter and a hostile platform with Bluesky.