This is the process, extremely simplified:

1. It’s 1970. You inherit $10M from your rich dad who worked hard.
2. Buy $10M index fund stock.
3. Borrow $10M against stock.
4. Live tax free off that $10M loan for 30 years (you can do that because you started in 1970 when it was cheap to buy a house).
5. Your stock is now worth $58M (avg 6% per year for 30 years)
6. Your kids inherit the stock at its current value and immediately sell $10M worth to pay off original loan. They pay no capital gains tax because the stock barely moved in the time between when they took ownership and selling it. All of the value growth since original purchase in 1970 is now tax free. The kids now start with $48M.
7. Repeat

Obviously, there is more to it than this. For example, this does not account for interest in the loan, or diversification of investments, or ability to hire accountants to maximize on the process.