Consider the following scenario:
Say the interest rate for a wealthy individual like Bezos is 1% per period.
Case A: Bezos sells $100 of stock. He pays 20% and consumes $80. NPV of tax liability is $20.
Case B: Bezos borrow borrows $80 to spend in a period and then at the end of the period sells $101 of stock to pay back the loan and (and pay taxes on it). Thus his tax liability at the end of the period is .20*101, which in present value terms = .20*100 = $20. Exactly the same amount of taxes he would have paid if he didn't borrow.
Case C: Bezos sells only $80 of stock and then borrows $16 to pay his taxes, ending with a debt of $16.16 at the end of the period, and he will need to sell $20.2 in stock to extinguish his total liability ($16.16 due the bank and also the $4.04 in taxes on the sale), which in present value terms is the same payment as before, namely $20.
The real reason people like Bezos borrow to pay their taxes is because the interest rate charged to them by the bank is less the growth rate of their assets. Therefore they are acting like a bank, borrowing at one rate and investing at another rate, making money on the spread. Thus keeping the stock is worth more to Bezos than borrowing to pay the tax, which is effectively what is happening.
At least, this is what they believe. Of course this type of balance sheet expansion comes with risk - risk that they bear that if the stock price falls, they will end up paying much more than if they hadn't levered up and borrowed to pay their taxes. But that's a risk they are willing to take.
So you don't need to pull your hair out worrying that Bezos is not paying taxes. He is effectively borrowing to pay taxes so that he ends up with a bigger payment down the road, which in present value terms is the same tax liability as if he didn't borrow. The treasury will receive not only all the tax money as if Bezos never borrowed, but all the tax money with interest, namely whatever interest Bezos needs to pay. However Bezos is betting that the growth rate of his assets is even higher. So now you understand why everyone is borrowing to pay taxes -- because interests are so low. So thank the Fed that this type of arbitrage is possible. It's not tax arbitrage, it's interest rate arbitrage.