The fired employee named the executive, on Twitter, in the same thread before being fired.

And, Twitter, as you're all probably aware, can be a cesspool of under-moderated hate, lately.

The company and executive should reasonably expect that the executive will receive a lot of hate from randos, due to the tweet thread.

I suspect this tweet thread opens Unity Inc up to risk by funding, through keeping on the payroll, a person who, in turn, drives hatred and vitriol online to another one of its employees. So I imagine unity decided to put an end to this liability.