The answer is money

Cutting off Twitter means losing potential audience. It was an ideological stance when they did it, now nothing ideological is left at MozCorp.

To me it seems like they're really pushing for mass-market appeal right now compared to just maintaining or slowly growing their existing more dedicated/niche base.

You can see it with them adding widgets, a free VPN, more visibly advertising trackers blocked (at least on Android, not sure about iOS), rebranding with a new mascot, and now going back to a platform that still has a ton of user lock-in keeping people there. They're trying to pull in regular people, I presume so they don't become as dependent on a base that has more strongly held convictions that Mozilla has to comply with to keep its users.

If it works out for them, it'll be good for their long-term funding and security, market appeal, etc, but bad for users that care a lot more about fundamental principles.

There's potential users there, and ff isn't going to lose any users by rejoining.

AI?

Sadly plenty of ppl still use Twitter, plenty of companies and celebs still doing their thing there. Why do we have to single out Firefox? It's not a company that as ideals like most people here do. Yeah their new stuff is definitely shady, but it's that for Chromium. I'll still use Firefox, this doesn't bother me at all, cuz honestly who gives a fuck. I get the optics, but we do not live in a perfect world of morals and ideals. I only have limited energy I can dish out and this affects me 0% so I'll put that much into it. People are addicted to being angry all the time...