Some foundations have been used that way, no doubt. But I think there's a difference between setting up a tax shelter with vague goals and actively committing to spend down the entire endowment in a specific timeframe

True. Actively committing to spend down the entire endowment in a specific timeframe does not mean it is not used create a dynasty.

In the 50's the Congress in US was getting suspicious about those foundations already. There were a investigation for it:

https://en.wikipedia.org/wiki/United_States_House_Select_Com...