It seems to me that you're speaking a bit past heipei's question, which is about the actual consequences, as opposed to the intended ones, of policies.
If you have a 90-100% estate tax, then the intended consequence might be "redistribute the money via the government" but the actual consequence is much more likely to be "most of the money is spent on luxury consumption, because why not?".
At lower levels of estate taxation intended and actual consequences might align better, of course. This is pretty specifically a question about calls for near-100% estate taxation, not a question about why there's an estate tax in general.
If you have a 90-100% estate tax, then the intended consequence might be "redistribute the money via the government" but the actual consequence is much more likely to be "most of the money is spent on luxury consumption, because why not?".
At lower levels of estate taxation intended and actual consequences might align better, of course. This is pretty specifically a question about calls for near-100% estate taxation, not a question about why there's an estate tax in general.