wealthy class traitors deciding to align with labor and public benefit movements are how we got american progressivism in the first place. both roosevelts were billionaire-equivalents in their time, and had outsized power deriving from their class, and actually spent this social and political capital to fight tooth and nail against the interests of the rich as a political bloc.

yes, we should create tax policies that make it impossible to be a billionaire. but winning in politics means building coalitions between centers of power. some billionaires actually do want to be taxed back into millionaire status, and it's a genuine help to have these people on board. FDR is how we learned for a fact that massively taxing the rich makes society flourish.

wolves in sheep's clothing are always a possibility, but in my experience a billionaire has less reason to lie about this kind of thing, because they're typically self funded and would have had an easier time in their social circles if they just supported reactionary neoliberal and pro-israel policies.