From what I remember they were using GNOME for pop os with some custom addons they had made (for example a tiling addon). GNOME updates will sometimes break addons and I think the pop os people got tired of this.
That's barely a footnote compared to the development time that writing an entire DE requires, not to mention that now they can't piggyback off GNOME's development anymore and they'll have to do everything themselves. There's a reason Ubuntu eventually abandoned Unity and came crawling back to GNOME.
rust implies performance and security
Rust implies only 1 thing, and that's no memory leaks, assuming you don't use "unsafe" code. It's still very much vulnerable to logic bugs and has the same performance as c (GNOME) and c++ (KDE).
Parents fail all the time, that's when the government needs to step in and take action, in this case by making sure kids can safely play the game. And I disagree, Roblox's entire business revolves around children, they make money off them at every step and they even pay kids to make content for their platform; they should be and they are rightfully being held accountable for what happens on their platform.