From what you're saying, it seems as though the company is damned either way. If you have earned a lot of market share, it doesn't matter whether you charge a high price or the lowest price ($0). Or is the answer just that when you reach a certain size, you should just be killed, never mind the cost to everyone else (including customers that depend on the products being offered as well as employees who have built careers working to make the company successful)?
Large companies don't do everything well, to be sure. But who is going to go out on a limb and fund the big bets, like Xerox PARC, Bell Labs, MSR, etc. if we keep cutting down the tall poppies? Academics have a place, but there are structural organizational and social reasons why they were not able to invent everything we enjoy today.
Folks wanting to know more about Bell Labs can check out "The Idea Factory" by Jon Gertner.
Imagine if Apple bought Intel. It would be extremely likely that Intel would be forced to continue to sell its products to everyone, even if theoretically Apple might want to just stop shipping the parts to competitors.
It's a $1.5B company now (not monopolistic/huge, but a nice business...)
Monopoly by definition is a single (or overwhelming) supplier. Vertical integration is about the exact opposite since it opens the business up to competition all along the supply chain. Amazon now competes with almost everybody.
We've had larger firms in retail and other industries in the past that died of natural causes. There is no reason to think different of modern tech companies. These are just the people who are getting the transition we have in the marketplace. Others will see and pick up on it to. You can't judge a monopoly over just a 10 year period of time.