Do we want company's to dominate an industry because they are pumping in money from their domination in another industry? A unprofitable business is a failure and should be replaced by other firms with better business models
Capitalism is the principle that you need capital to pay for things. If you have more capital than a competitor, you can sustain losses for longer, until your competitor runs out of capital to pay for things like food and has to stop competing.
The principle of capitalism leads to competition, but it's necessarily only temporary. Eventually, capitalism inevitably leads to lack of competition.