By borrowing against their holdings. The framing is deceptive. You can do this too: there is no requirement to have billions in collateral. If you own stocks, your brokerage will lend you money at a very low rate, secured by the equity - typically up to about half of your stocks' worth. The gotcha is market risk. If there's another crash akin to the housing crisis - and there will be - the bank will liquidate your ho…
I disagree the framing is deceptive. A big reason this is done is to avoid paying taxes altogether - borrow against your equity, and then when you die your heirs receive a step-up in basis, so the gains are never taxed. To make it worth while you need to have a crap ton of money, such that the interest on your loans is less than the estate taxes you'd pay. Only very, very rich people pay any estate taxes in the first…
That's federal estate tax. State tax can be different. Massachusetts, for example, has estate taxes on over $2M ($4M for a couple who manages their estate plan wisely).