And I am not going try to convince you in a popularity based forum, but that is generally the objection.
You are saying that this gives more power to google and someone asked if you could elaborate on why you think that. Not everyone has the same background and what may be obvious power to you may not be to others. This forum is supposed to be participated in with good faith.
But on the other hand meta isn't that interesting either. If large companies wanted to do security research that wasn't objectionable to people they could do so by consensus, standards and agreements. No one could really question that. Instead the idea is largely that "the ends justify the means". That is what people tend to disagree with. That large companies can unilaterally decide how things are done, not just for themselves but in a way that affects other companies or their users. It doesn't really matter if it is for good or best practice because it is about them, especially as large companies in the industry, having that influence.
And if you rule out "all companies like Google", you've basically ruled out everyone with enough capital to donate to research, depending on your definition of "like Google".
And really, it absolutely is a donation. The ROI on Project Zero is likely 50x or more less than if that money went to the marketing team.