This same exact thing happened to the blind community, of which I'm a member of. Blind Twitter was pretty vibrant before Elon took over, but that changed almost completely around November/December of last year. The killer change for us was the death of third-party clients, on which blind people relied almost exclusively. The whole community is on Mastodon now, mostly concentrated around two instances, though there are plenty of people elsewhere.
All of the infosec people I follow have moved to Mastodon. As someone with primarily tech related interests, I'm currently finding Mastodon as good or better than Twitter at it's prime.
Infosec twitter may be gone, but the infosec spam bots are still there. Just try searching for "Linux kernel" and try to find content by a real human. Before you manage to find one, you'll have to scan through hundreds if not thousands of low-quality bot posts about the latest linux kernel commit, linux kernel CVEs, or linux kernel mailing list posts.
I for one welcome the decentralized internet that Elon is ushering in. Things were better when we had small disparate forums where people could develop their perspectives in community. As long as people are members of multiple communities we should have enough cross-pollination and course corrections to keep things mostly on track.<p>Mods and groupthink are always a threat but it turned out they were a bigger threat still when everyone was trying to be on one social network to rule them all.
This is sad indeed, but it was already infested with low quality trolls before the Elon Musk purchase. The entire Jonathon Scott clown-fiesta was utterly embarrassing.