I also support 100% inheritance tax, but it's not something I believe could be implemented unless it was already normalised, which is a bit of a catch-22. Ultimately a huge driver of inequality is the fact that some people start with a leg up over others already, and the people who want to leave their kids 50k or whatever are enabling the ones that are leaving theirs 50m and an undeserved life of privilege and influence.
Did we learn nothing from the rich bullies of 80s teen movies?
It's not their money, and in the long term I think it does far more harm than good to society to move it down the family tree (at a macro level, it's responsible for dynastic disputes and civil wars). Even if you effectively abolished cash inheritance then the scions of wealthy families still likely benefit from their parents wealth via a more stable upbringing and more opportunities for travel, making contacts, so on.
Would never work though, the money would just be hidden away in trusts or something even if you could overcome public opinion and the desire to help out kith & kin.