Why isn’t the PoS algorithm an Argumentum ad Crumenam fallacy?

The PoS algorithm works as an alternative to PoW with the purpose of reducing the energy consumption of operations based on protecting the system with its own wealth instead of work.

The philosophy of this is that the person who has the greatest number of wealth in the system is the one who should be concerned about its security, however, would this not be a fallacy "argumentum ad crumenam"?

We could say the same sense of government institutions and bankers that are the ones that have the greatest wealth, however we all know that those mentioned are an human disgrace and that was the initial reason for creating cryptocurrencies in the first place.

I'm not saying that the PoW algorithm is a perfect alternative, especially to the 51% problem, but I think that with the PoS algorithm, not only would it make you more vulnerable to such an attack, but it would make the rich even richer and monopolize the market.