Ideally the stock market represents the real value (the equity) of companies. To use an idealized example: If a company is worth a hundred million dollars and has issued a hundred million shares, then each share is worth one dollar. If someone wants to buy my ten shares, I should be happy to sell them off for ten dollars.
If that company is doing really well and its profits will double its worth to 200 million dollars, then each share is now worth 2 dollars. If someone wants to buy my shares, I'll tell them that it will cost them 20 dollars, not 10. But... why should I sell? The company's doing great. I expect its value to continue to grow. In one year it grew 100% and so did my investment in its stock. I'd be crazy to sell off my stock at the new value of $2 a share. But the person who wants those shares also wants to get in on the tremendous returns in this company, and so, they offer more than the current value. They may offer to buy them at $3 a share or $4 a share in the hope that years later, they can reap the large return on investment.
And that's how shares become divorced from their "real value" of equity divided by the number of shares. They get bought at higher prices by people hoping the company will grow and increase their investment. If the company looks like its failing, they'll be ready to unload the stocks at a discount/loss.
So, let's consider Disney. During a time when so many big name companies are filing for bankruptcy (e.g., Lord & Taylor) and the expectation that Disney would be in horrible condition thanks to parks and filming production closing down, it turns out that Disney's operations turned a small profit! And Disney has ready access to $40 Billion if they need it (plus even more if they have to). It's clear: Disney can weather a full year of COVID while other entertainment empires and many other businesses may collapse. Disney stocks are safe. And when COVID is over, Disney is poised to fully rebound (even if it takes a few years because of a recession).
If you had to buy stocks right now in the hope that they will rise to where they were before COVID... where would you put your money? People are betting on Disney. And the rush to grab Disney stocks is pushing the cost of stocks higher and higher. People who have the stocks shouldn't really be wanting to sell. So, brokers are bidding higher and higher to convince current holders to sell.
The market buys and sells based on what the future is expected to be, not on current value. Speculators, who aren't interested in actual worth of equity, are just trying to game buy-low-sell-high as quickly as they can, which makes the ups and downs greater than they should be.