That isn't a surprise really. Many new aspiring millionaires are still driven by greed. Once they break the $10+ million mark they start to give more money away because they realize they can't spend it all. Many very wealthy people, $500+ million, donate a lot to charity so they don;t care about a little more tax.
And they have really good accountants...
True but most business people, large or small, find ways to minimize their tax bill. I had a relatively small business for a decade and my 'true' earnings were at least double my declared earnings.
Many 'super' rich actually start giving huge amounts of money away. Buffet, Gates, and many others donate billions to charity, which is great, BUT many of them help overseas causes, which is not so great when they earned much of their fortunes off the backs of American workers.