> Are celebrity endorsements actually useful for building trust?

I can't imagine this is highly controversial. Of course celebrity endorsements can be useful for building trust. This is supported observationally and by years of research in marketing psychology. It's not even necessarily limited to megastars : even endorsements from niche influencers and small-fish content creators can be marketing goldmines, nevermind the kind of overnight headwinds your product can get if someone with the reach of Oprah, Rogan, Musk et al starts pushing it.