There isn't anyone with enough money.
Just to by a simple suburban street takes millions and millions.
Even someone with the cash resources of Apple could maybe get one or two suburbs of San Francisco before the prices started rising fast and they priced themselves out.
Cornering a market happens periodically in small markets like commodity futures or stocks in a single company - and usually only for a brief period.
You could make the argument that you could 'buy' a government by buying all the available currency. Technically it's true but practically it's not. Who would want to own a monopoly in real estate anyway? People and businesses are sticky, but not stuck. If the rents got out of hand they'd just move.
Best to start when the land is cheap, and when you are going to build infrastructure to increase the value of the property. So the railroads with tracks and stations, amusement park operators (Disney World...), or it could be a factory with lots of jobs in a depressed area.
I'm curious, has it really happened at a city level? Seems to me that it would get prohibitively expensive, since other owners would see the massive demand and push up the prices, but that's really just a supposition.