It doesn't. There's a movement (no idea how well known this is) to not engage with toxic people that have a check mark because they can get money from twitter for that. Hiding the checkmark is most likely for that purpose; keep engagement, thus keep money flowing toward hate groups.
No one bothered to answer you, so I will try: Since the takeover by Musk, the group who felt the most emboldened where people on the right spectrum, because of what Musk is putting out on his feed. It's mostly stale memes, retweets of stuff his other companies do and tons of right wing stuff: Tucker Carlson is just the most famous but his liked feed is filled to the brim with obscure assholes! It's insane! If you don't believe me, there are videos on YouTube where people sift through his feed and it's just maddening, how such an idiot could become one of the richest people in the world!
Anyway, to answer your question: alt righters usually cheer on most of the stuff Musk is implementing, with the blue checkmark definitely being one of the main "signs" they wore with a certain pride and as a sign of support of Musk.
I guess now Twitter (I refuse to call it anything different!) has become so uncool even in the cringiest corner of the right wing that they have to give them the option to turn it off otherwise they will cancel the subscription.
Musk behaves like an alt-right idiot. Anyone who wants to give him money, must be an alt-right idiot too. Not that hard to figure out. Now people are shaming them for giving the alt-right idiot money for a blue mark on their profile. And since they are very, very fragile snowflakes, they now can hide it to keep from being taunted. But they still must give Musk money for the blue mark they hide