At least a couple of factors. The first major thing is that It seems like many people are no longer really moving away from X no matter what Elon does or to the extent they do the hype for Bluesky may have died down so much that they go more to Threads. Ppl leave as the site slows down.

Another factor is a string of bad mod decisions and interactions that the BSky team has had with the community which has made people think they may not really be that much better than Meta or X

@200ok @bluesky