> They didn't have to join, which means they got a solid valuation.

This isn't really true. It's more about who wanted them to join. Maybe it was Anthropic who really wanted to take over Bun/hire Jarred, or it was Jarred who got sick of Bun and wanted to work on AI.

I don't really know any details about this acquisition, and I assume it's the former, but acquihires are also done for other reasons than "it was the only way".