the baked in incentive to hoard capital to produce commodities at lower prices / monopolize to charge higher prices

That is something Marx will talk about a lot, in detail, later in the book, especially in "Part VII: The Accumulation of Capital." He actually gives a down-to-earth, simple example of one business owner who has X amount of profits, spends Y amount on himself, to buy a house, diamonds for his wife, toys for his kids, dinners at fancy restaurants, etc., and then invests X - Y = Z back into the company. Modern corporations are much more complicated than this, because they have thousands of investors, or even millions somtimes, if we consider Vanguard-esque retirement funds. But yeah, Marx basically sees most industries as naturally tending towards monopolization. That is one of the main differences between Marxist and liberal/libertarian economics. You can't compete your way out of this problem.

Furthermore, many Marxists in the past 150 years have predicted that this tendency to ever-more monopolization and increasing "economies of scale" for large corporations will lead to a race to the bottom, with rates of profit continuously falling across the board. Some Marxists even believe falling rates of profit will be the main thing triggering the next big worldwide war/revolution, although that is a hotly debated topic.