I beg to differ... I think oligopolies are due to the government making it difficult and expensive for new businesses to start.
Existing businesses frequently work with the government to create as many laws and administrative burdens they can, to keep the competition out.
I am a small business owner, and based on my experience of doing business in northern europe this is the case.
At the extreme macro level, you can see how banks utilize this. Banks today are basically
@ChrisMayLA6 a private arm of the government.
On the other hand... if you are driven enough to break a monopoly of the government, or an oligopoly, there's plenty of cash to win!
Jan Stenbeck of sweden, smashed the government monopoly on telecommunication and TV in sweden, and it made him a billionaire in USD.