Almost all of these uber rich hold assets as shares in enterprises they manage with mutable value. They don't diversify most of this wealth into other people's stocks. Their investment is motivated to enhance the underlying value of the enterprises they control. Bezos owns Amazon. He's not now owning chocolate factories, Microsoft and a uranium mining enterprise. He owns AWS and .. selling other people's things. Musk owns his cars, his batteries, and his space enterprises and X. He isn't visibly acquiring Ford, or the Indian National railways, or banks in Japan.

I'm not trying to disrespect this. I just want to observe it's ephemeral wealth tied to the stock price of enterprises they own. Diversified stock backed wealth, land, minerals, food production is somewhat different. Some of that is also somewhat ephemeral wealth, agriculture is notoriously variable to its value against climate.

Should spaceX undergo some unforeseen launch related major problem, or tesla become ensnared in a major lawsuit, or xAI and C underlying debts get called in a LOT of this wealth would evaporate surely?

What I read suggests space X is immensely valuable on government contracts and starlink and xAI is a major debt overhang, which won't entirely vanish because of this float. Instead, it will be diluted into the general stock purchase. If Musk hadn't restructured the AI debt into a bundle, this would be more clear.

Carnegie owned steel. He sold out for the equivalent of $300b or more and then gave it away. Buffet owned the entire market and made profit in re-insurance. He was across everything. (He's retired now and also appears set on giving almost all of it away)