To put it bluntly, this is because of the Federal Reserve. Fundamentals refers to the ability to generate a steady return of profit. This goes back to Graham and Dodd, “value investing” (“the intelligent investor” and “security analysis”) and the perspective of a long term investor where all investments are fungible according to their risk adjusted rate of return.

But since the government can’t fund itself on revenue, but relies on the central bank printing money, all this new currency flows into the economy and into the stock portfolios of the upper classes, which inflates the price of the stock faster than the business can generate a profit. Which means all the old value investing stuff doesn’t tell you how to make the most money anymore. So the “fundamentals” have changed and no one knows exactly what they are.