If you don’t recognize anything other than centralized vaulting as a cause of monarchy then your confusion is understandable.
Discussion
Not the only, but a strong influence keeping the average person from accumulating wealth and power that bitcoin eliminates.
In bitcoin all participants can join in equally if they choose, no single decider because they could be corrupted.
Monarchy says that person is better and in charge as fact because of who their parents were. History is full of stories of the monarch corrupting and turning against their own people.
History is also full of multi-generational benevolent monarchs. The oldest form of governance won’t disappear because of bitcoin. Making it hard or impossible to confiscate wealth will mitigate many of the risks of monarchy. It may actually get more popular as a result. Stability of a lifelong ruler and a clear responsible party who you can dispatch if needed? And he can’t take your money? Sounds pretty good.