And where did they get it from originally?
They inherited it from their father.
From conquest and the crown used to take anything it wanted only held back by fear of backlash from nobles. You are talking like this is some god given right.
No, I am not. I'm an atheist. Your god, whichever one that is, has nothing to do with me.
In order to be consistent, you would at least have to seize all assets with a line of inheritance going back more than a little way in time because if you go back further than a little way you will encounter something that would be considered unethical
by current standards. But you're not consistent.
The monarch "owns" it but if we have no monarch then there is no owner, its only Elizabeth Windsor's while she is monarch. It would no longer have an owner so it would be absorbed by the state. So no one is stealing anything. It's not like the Windsors wouldn't be left as porpers. You seem to be arguing that she should be allowed to keep it even if she is no longer queen.
And again, you're dishonestly advocating the seizure of privately owned assets by proclaiming that the owner of those assets doesn't own them because you say so. Everything I've said previously still applies. If I stole your car and proclaimed that it's my car and you never owned it, would that make it OK? Or would you still consider that theft? I would.
The current owner of those assets doesn't own them because she's the monarch. She owns them because she inherited them from her father, who owned them while he was alive. He in turn inherited them from one of his parents, etc, etc. Those assets are not owned by the state or by the crown. They're
managed by the state. More specifically, they're managed by an organisation appointed to do so. But they're owned by a person. The agreement was and is clear - the
income from the assets was assigned to the state. The assets themselves were not. Abolishing the monarchy would nullify that agreement, so the income from the assets would revert to the owner of the assets. Seizing the assets would be seizing the assets. Other things are owned by the crown and/or the state and would thus revert to the state if the monarchy was abolished. Including, for example, the duchies of Cornwall and Lancaster. But not the holdings
managed (not owned) by the Crown Estate.
Advocating revolution and seizure of assets by force is one thing. Doing so and pretending you're not is a different thing.