In most Western countries the ‘far’ left party can usually get anywhere from 5-15% of the vote. That kind of vote would sink the Democrats and maybe shift them, or at least the Overton window, leftwards. But I think third party votes in the US are much smaller right? At least for the left wing parties.
I don’t know how useful this sort of action is, although I don’t see any harm in bullying rich arseholes other than the danger that the activists expose themselves to. And at least here it’s targeted. Which makes it a lot better in my mind than the sort of stuff that groups like Just Stop Oil do, where they basically act against the public in general (things like holding up traffic, interrupting public events and so on) and which might as well be a psy-op for all the good it does