@molly0xfff The best way to learn about these was IMO to play Railroad Tycoon 2. The first part of the game is to build a railroad - the second is to invest in your competitors and to take them over. To do the latter it was very tempting to maximally use your leverage to buy as much of their stock as you could, re-maximizing when you got the chance.
That did mean that if they ever dropped slightly, you'd be getting a margin call from the bank, which resulted in forced selloffs. Which themselves cause the stock to drop a bit, making you further behind and getting another margin call .. until you have nothing left except for a debt.
I hope these companies are smarter with investing in real life than I was as a 16-year old gamer in a low-stakes game.