He is a betting man. He himself says he and colleagues bet against the economy in the financial crisis and made shit ton of money.

Stock market/trading is a kind of zero sum game. For him to gain, someone else has to lose.

However, real economy is not a zero sum game and I dont think he understands that. AFAIK never was an entrepreneur, or created a business.

He advocates for a wealth tax, ie a tax on unrealised gains.

For realised gains, we already do wealth tax and thats called capital gains tax.

I think he understands that but when you have a situation where the real economy is growing only around 1% per year but rich people grow their wealth somewhere around 4-10% that can only come at someone else's expense.

In other words while the real economy might be growing as a "non-zero sum game" the growth of the elite and the rich far exceeds that and outpaces it. Net effect is that their wealth is wealth away from everyone else.