They're not talking about natural monopolies. A natural monopoly is when there's some barrier to entry that prevents competitors from entering the market, like a need for prohibitively expensive infrastructure.
What OP is talking about are situations like Walmart opening a store in a new location, operating it at or near a loss to drive the local competition out of business, and then jacking up prices once no competitors remain. The government isn't forcing them to do that.
I made .iso files and mounted them in virtual drives to do the same thing. I could have used cracks but I didn't want a virus and I still had the delusion that doing things "fairly" actually meant anything.