Also, in the US, often companies offer you money to not sue them when they fire you. Doesn't mean the firing is legal, simply it is easier for everyone involved that way.
Here the guy was likely fired for saying that he witnessed discriminating hiring practices, i.e. quotas, to improve diversity metrics. And firing a whistleblower is illegal in the US as well. Most likely they will reach an agreement (or they have already reached). The guy will get some money and everyone will move on. Much easier than getting involved with legal stuff for both, google and the engineer.