The only stated reason for his resignation is that Google is no longer adhering to their promise to not use AI for weapons. I was surprised that the reasoning was so one-dimensional.
One of my favorite 80's movies was Real Genius with Val Kilmer. He accidentally helps develop a weapon and then goes to extreme measures to prevent its use. For some people creating weapons is a line they wont cross and that's not a bad thing.
Would the author have left if they didn't have another job lined up? Definitely not. Then, how strong are their principles?
That's not remarkable to many.