Though unlikely the case here, family foundations should always be looked at as a likely source of corruption.

You cannot bribe me directly - that would be caught. However you can donate money to my family foundation and my kids (or spouse) will draw a large salary from it while doing almost nothing and they do some good for the world so it looks like a charity. Of course the kids/spouse will support me in various ways that all rich kids will.

Again, probably not what is happening here, but every time you hear of a family foundation you should ask who they are using it to corruption in some form. Even when it doesn't seem to be you should still look.

Even very large salaries are probably not a very significant amount of wealth for these people. I think this is a case where "all large numbers look the same."

If Warren just directly gave his money to his three children equally, and paid 40% inheritance tax on that money, and then the children each just used 1% of that wealth per year, then they'd each get:

144000000000 * 0.6 / 3 / 100 = $288 million each year.

No foundation pays its CEO 10% of that much money. I think we may have to accept that in fact this is a way to give money to charitable causes, not just horde it.