[xtracto]

>If you really cared about the water problem, couldn't you have donated part of your (steady) income for that?

There's lot of scientists whose life objective is to solve a variety of world's problems and they don't want to become rich.

The point is, this guy did not want to be in a startup, he wanted to work directly on doing something to solve the World's water prblem. That's good for him, and IMO it does not make his decision worse than staying doing something that did not fully satisfied him anymore.