Monopolies are fine if they are not government mandated. The best example I have heard is De Beers, the diamond company. Even Standard Oil before 1911 was a monopoly that created consumer surplus. Ironically Standard Oil market share was 60 percent in 1911 vs 90 percent in 1890.

Almost every monopoly today is created by government: Post Office, Amtrak, public schools K-12

Government monopolies are terrible. Private monopolies can be beneficial for the consumer and rarely last for more than a few years.

What is the definition of a monopoly? Standard Oil had 60 percent market share in oil refining in 1911 when it was ordered to break up. Does 60 percent market share constitute a monopoly? Regardless, John Rockefeller did a lot of good for this country (and I am not talking about his philanthropy which was also extensive).