I think there are two things going on. After launch, there was an exuberant group of users who believed the purpose or aim of Bluesky was to be a recreation of Twitter in terms of user base and impact. They were lead on by the icon a bit and lots of rhetoric. And I think many believed it would destroy X. By their standards, Bluesky is an epic failure.
But by the aims of the company itself, moving social media from proprietary platforms to open protocols, it's a major success. And I think it can continue down that path and serve its users.
> And I think many believed it would destroy X.
Given what Musk did back at the time - member him carrying a sink? Randomly unplugging servers? - it was not that much of a stretch to assume the BS would eventually catch up with him and Twitter would enter the FO phase of FAFO.
Unfortunately, for unfathomable reasons Twitter is still alive somehow, despite being a cesspit of Russian propaganda, far-right propaganda, general trolls and a ton of porn sellers... I frankly assume the porn is what keeps a lot of people on there instead of Truth Social or one of the countless other attempts.