The following three things help large corporations establish monopolies.
Big government. The bigger the government, the more favours the government can grant. (The more money there is to be made from government, the more corrupt businesses and politicians tend to be.)
Excessive regulation. (Some regulation is necessary. In China they have almost no regulation (see here), allowing almost anything—including dangerous work practices and the theft of intellectual property. The guiding principle seems to be that if it benefits the CCP, it is allowed. In many ways—despite China's totalitarian government—China is the most laissez-faire economy in the world.)
The following video explains why big business in generally is behind excessive regulation in the West. (Watch from the 22nd minute. Click “Watch this video on YouTube” below.)
A good example of how big business manipulated government and pro-consumer groups to get their way, were the railroad monopolies in America. Milton Friedman explains how they did it here. See also.
The final way big businesses establish monopolies is counterintuitive, but just as important as the other two.
A good example of how big business uses the minimum wage to crush their smaller competitors is Amazon. Amazon paid their workers little, but after pressure generated from the media raised their workers wages. But immediately after raising wages, they started lobbying the federal government to increase the minimum wage. Being far more mechanised, Amazon does not have to pay as much in wages as their competition. They know that a higher minimum wage will hurt their competitors, making it easier for them to establish a monopoly. See Why Some Capitalists Are the Worst Enemies of Capitalism.
Crony capitalism (corporatism) is the problem. (Few know this, but what the World Economic Forum describes as The Great Reset, is an attempt by many of the largest corporations in the world, to establish an absolute monopoly, a kind of international mercantilism, that can never be challenged. They say they need to do this to increase efficiency and save the planet. They are doing this with the help of the most powerful economies in the world. Part of their program involves giving countries and corporations ESG scores, and granting credit to those with high scores. But the whole thing is a scam. China has a very high ESG score and Tesla a low score, because Elon Musk (at the time of this writing) has not been playing their game. See China is painting Mountains Green to fool Environmentalists - No, Really and the two part documentary The Great Global Reset.
We need a return to small business. When there are lots of small businesses, and many of them are growing, that is a sign of a healthy free market economy.
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How Wall Street Sold Out America
Thomas Sowell destroys the Trickledown Argument
The Government Against The Economy