Firstly it shows the value of individual shares multiplied by the number of shares, not the company as a whole. Secondly, in this case Nvidia’s share price is based on what the company may be able to expand to do in the future, not what it currently does. Thirdly, where would this repersentive percentage come from? If it’s, issueing new stock to employees, A Nvida already does that a lot, B, creating new stock is not practically reliant on overall market cap so why is it relevant, and C, would employees also be punished for destroying the valuation if it turns out that every company doesn’t actually need a data center full of several thousand AI accelerators scraping the internet to make unique chat bots and Nvida’s market cap falls back down to what it would be based on how much money the company actually makes?

Again, Nvida primarily makes chip designs for outsourced fabrication, not market cap, that three trillion isn’t like revenue for Nvidia. In your painting example, market cap would be like if two unrelated billionaires bet 10 billion on whether or not that painter would be successful in selling a hundred different 1m paintings in the next six months, the painter might have an easier time say getting a loan for new supplies from a bank if they can point to the billionaire betting so much on them, but you know it’s not like the painter was actually paid that 10 billion that makes up the bet.