Just read the post! It's essentially "we switched from Radix to Base UI". Why? "the ecosystem moved on". Nothing says braindead web frontend churn like this post, and them not having written it in the first place is just the cherry on the cake.
They could have just written "we asked Claude to rewrite our project with Base UI because it eclipsed Radix in NPM downloads".
If you're not a heavy frontend developer then you probably don't know why radix is a blocker for most server side react