They built something amazing and now have a nice exit. The code remains open under a non profit foundation. I don't think it is that bad. If working conditions are too bad people will just quit and work for the foundation.
These kind of arrangements generally get the investors their money back plus a modest return. The employees generally don’t get much, relative to the risk they took.
Is profit sharing, like what you're implying, actually happening? If so, in what quantity?
Buying the team and having them all quit is such a bad outcome for AWS, especially they would not keep any of the IP, which is owned by the DuckDB Foundation. I don't think they would be that short-sighted.