It's pretty hard to discuss such things without people getting emotional and defensive. I think people look at something like this and say "but that's not fair I earned all my money"[1]. They don't look at it and think about what the world would look like in such a scenario, how they might have lived differently, how they would instead spend their money before death (perhaps making the world a better place), or how they might have less concerns about needing to pass on money to their children because their children would be "just fine" in the society they created under this system.

[1] ignoring the whole subject about luck and what it means to earn something when two equivalent folks just have different dice rolls go their way, etc. Or especially in the context what it means to earn something when you just inherited it. (I have a bunch of friends who have inheritance coming their way and just totally expect it, they lead very different lives because of that than those I know who don't have that.)

It wouldn't actually work. Rich people end up finding loopholes to any tax scheme. Even if that loophole is expatriating.

It would have negative consequences besides that. Many, many people do things for "legacy". It's a powerful motivator. Taking away all wealth would eliminate something that encourages good long-term decision making.

It would hurt people who aren't the rich people. What would happen if Sam Walton's net worth was taxed when he died? Massive disruption to Walmart employees at a minimum. How would the net worth be calculated? Well, given his net worth, he'd be irresponsible not to have an army of lawyers and lobbyists making sure the number is as small as possible.

So, given the above, the idea isn't that simple.

Finally, there are ethical implications to that sort of policy. It implies that citizens earn at the pleasure of the government, not that the government rules by the consent of its citizens.