If Bluesky is a "liberal bubble," it could be for the same reason it's a "heliocentrist bubble," an "evolutionist bubble," a "science-affirming bubble," a "non-racist bubble," a "Holocaust-affirming bubble," etc. etc. -- because we've been proven right and those who are wrong don't want to be here.
Bluesky is a "liberal bubble" because fascist chuds can't get traction without algorithmic assistance and because people here trained themselves to block "debate me" trybois the instant they roll up