For the individual wealthy, they aren’t. Some loans might get paid off by taking another loan, but the goal is to take the loan to the grave. The loan would get paid after death because then the estate can sell the stocks without paying any capital gains tax.

Let’s say you buy 1 million worth of stocks. The day before you die that stock is worth 51 million. If you cash out that stock you’re paying capital gains tax on 50 million. Let’s say the capital gains tax is 20% which means you’d pay 10 mil in taxes. So you get 41 million from the sale

But if you die and that stock goes to the estate they haven’t gained any capital from the stock so when they sell it they pay no tax on it. The estate then sells the stock tax free to pay off whatever debt there was and the rest of the stock goes to the inheritors who can effectively continue doing the same thing.

Basically it’s all just tax evasion for the ultrawealthy. Except it’s legal so technically it’s not tax evasion.