Pretty much how Bluesky took off at all. It's just the polarization of the platform style reflecting the polarization of society: Twitter/X went right-wing so the (center-)left made their own platform. It's the same thing the right did when Twitter was politically censoring right-wing content before Musk bought it and Trump made Truth Social, the only difference being that Bluesky got the Big Tech and mainstream media blessing. Musk said he would stop that sort of censorship but just reversed it to censor left-wing content. Nobody actually wants a truly free platform, they just want their echo chamber.