Legally speaking, Google is aiding surveillance which itself is questionable, of a foreign population whose colonisation is internationally declared as illegal.
The slide visible on the video also indicates the use of AI in their solution which they KNOW is being used in the war.
Legally and ethically we are absolutely not in a gray area, it is quite clear that Google is knowingly participating in something illegal and unethical.
That is beside the point but he surely no longer wanted to be part of the company. So it was either quit or get fired. I guess with the latter he can have unemployment benefits.