I doubt that the FB people involved with the layoffs are the same FB people who decided to open source the Sapling project. Many FB engineering managers were not aware that the layoffs were being planned. Moreover, it takes up-front planning and design decisions (by more than just a few days) for a private company to open source their internal projects.
The open sourcing schedule was completely unrelated to the layoffs.
The team working on Sapling has been planning this release for a very long time and will continue working on Sapling to support our internal engineering efforts.
Was bulk of the team behind this laid off wherein it made sense to open source it to involve the community to take it forward rather than paid resources?
To be clear: I'm NOT criticizing them open sourcing this.