"They should be allowed to get as big as they want, as long as they do not become either a monopoly or an ologopoly." But they do. First they squeeze out the little businesses, then they jack up the profit margin when they've squashed the competition.

"If businesses are not profitable, they cannot stay in business" - profitable means two thiigs. It can mean not runnig at a losss. And clearly you can't run at a loss, without some kind of subsidy. But it can also mean, and it does mean, maximising profits, and offloading costs (such as environmental costs) on to other people. And it's quite possible to stay in business without maximising profits.

Most of the time in normal life that's how people operate - if a neighbour asked you to do their shopping, because they couldn't get out, you'd expect them to pay for the stuff you buy; you might expect petrol money; or even conceivably something to pay for the time it took you. But you wouldn't find out how much it would cost them to get it done using a cab, and jack what you charged up to fractionally below that, to "the market price".