Nuclide has always had a ton of value for Facebook itself as we could build a lot of Facebook-specific integrations and ship a new version to all the developers every week. It's now the most used editor at Facebook.
This announcement is about the open source version of Nuclide, which has never received a lot of love and didn't have a lot of adoption.
- dev env onboarding takes a minute instead of a week
- employees can code "on the go"
So predictably, if they get rid of Nuclide there needs to be an alternative and doubtful they've built something new because... why.