This is not about opposition to private property. I’m fine if people own a house, or a family farm, or a small business, or even a controlling stake in a large business they built from nothing. (Though it would be great if at that point the public had transparency into their self-serving political activities.)
But passing billions (and the derived political power) down to descendants several generations removed who did nothing themselves to deserve it is ultimately a recipe for a deeply broken society. It creates perverse incentives away from long-term thinking towards large-scale fraud and abuse, and entrenches the political influence of an aristocratic class whose primary goal is to maintain their fortunes rather than contribute to the society.