You'll get a lot of answers, but I think The Tendency of the Rate of Profit to Fall[1] is key.
Capitalism means competition. Competitors mean reduced profits. As we get into the later stages of the game, that pesky competition aspect comes into play and firms do whatever they can to worm their way out of its consequences.
As profits inevitably fall, firms flail around doing whatever they can to maintain them and cause all sorts of misery for employees, customers, and the world at large. Increasingly brutal exploitation of workers, rotting product quality, all sorts of shenanigans with regulatory capture and rent-seeking as firms try to avoid competition and the need to sell a quality product at a competitive price.
Capitalism means competition. Competitors mean reduced profits. As we get into the later stages of the game, that pesky competition aspect comes into play and firms do whatever they can to worm their way out of its consequences.
As profits inevitably fall, firms flail around doing whatever they can to maintain them and cause all sorts of misery for employees, customers, and the world at large. Increasingly brutal exploitation of workers, rotting product quality, all sorts of shenanigans with regulatory capture and rent-seeking as firms try to avoid competition and the need to sell a quality product at a competitive price.
[1] https://en.wikipedia.org/wiki/Tendency_of_the_rate_of_profit...