Cantillionaires have the ability to change the rules of the game itself in the fiat system. With bitcoin, it doesn't matter how much bitcoin a person owns, they can't vote, can't provide network security by staking, can't collude. They have within the protocol, as much power as someone with 0 bitcoin. The protocol (set of rules) are not different for a person with 10000 BTC than they are for someone with 0. Bitcoin is not something you can simply print more of, or invade a country and take. You have to work for it, even if you mine, it requires capex and a continuous expenditure of resources. And even here, it may or may not be profitable at times. The monetary policy of bitcoin is fixed, it isn't fixed in the cantillionaire fiat world. It isn't fixed with ETH. Distribution of ETH is absolutely a threat to adoption, because their block 0 was a premine block. And now with PoS, ETH gives token holders powers within the protocol itself. Without doing any work, or expending any resources, a staker simply acquires more and more power within the system, and the prospects of collusion get better. This is exacerbated by the ability to use derivatives within the system (LSTs et al), which can be derivative stacked to control more of the consensus.

Bitcoin is different, block 0 is inaccessible, as it violates consensus rules not pointing to a previous block, and the price of bitcoin when it began in Jan 2009 was zero. It remained zero until a rando decided to pay a guy in BTC to order him pizza a year later. This isn't the case for any other project, which has never overcome this bootstrapping problem. The distribution of bitcoin is incredibly fair, and directionally, will continue to distribute. At some point a person holding a bunch of bitcoin will swap it to capture some economic expansion (goods or services) outside the system, and because of its disinflationary nature, this will benefit whomever holds it next, who over time will be able to capture even more economic expansion than the previous person. If a person holding a bunch of bitcoin doesn't distribute their bitcoin, they simply benefit everyone else holding bitcoin, without any ability to alter the game's rules by leveraging time.