This will boost Ethereum's popularity with Vitalik doing humanitarian effort and 1 billion isn't a measly number that you just donate, I am sure that Vitalik thought of it thoroughly. And not to mention that this donation is also useful for him since it will be tax exemption for him.
This is not humanitarianism. He is giving away useless tokens. It is money created out of thin air and given to him for free. It is performative charity and nice publicity for ethereum but it is an action that cost him nothing at all. We should instead be praising people who worked hard for their money and still decided to contribute a significant portion of their income to helping others.