Someone with a net worth of $100 billion doesn't have one billion $100 bills. They have assets: land, equities, and machines. And they tend to also have lots of debt, because they can borrow at ultra low interest rates, which allows them to acquire even more assets beyond their net worth. Inflation helps them because leverage is cheaper for billionaires than for anyone else.
Someone with a net worth of $100b would be well advised to keep it as $100b in bills in a deflationary environment though, because other more productive things they could be investing in would, on average, return less money.
Deflation is everybody else working harder than last year to beg cash hoarders to spend their money back into the economy.
