Well, I wouldn't go as far as to say that a natural monopoly doesn't exist, but I think it's pretty clear that big companies have a lot of influence on the government, and typically can lobby the government to pass policies that benefit them, and make it harder for competition.
And I think there's an argument to be made that if the government were less powerful, then there would be less potential harm done when a corporation is able to influence the government.
I'm personally torn on this, because on one hand I think the government can be a useful tool in preventing monopolies, but on the other hand, I think expecting the government to not always work in favor of big companies seems naive.
Buying out competitors isn't a sustainable long term business strategy. Think about it, if one company was trying really hard to be a monopoly and simply bought out all their competitors, then anyone could make a shit ton of money by just continuously opening new competing businesses and selling out.
Secondly, if the strategy is to price out competitors, then... What's the problem? If the so called "monopoly" has to keep prices literally so low that no one else can compete, then they aren't doing any real harm. If they do eventually decide to jack up their prices, then that opens the door for a new business to open.