Because Rockefeller colluded with railroad companies and had secret arrangements to get bulk discount for himself and shafted his competitors.
- there is absolutely 0 wrong with providing a company with a promise to buy scheduled services on the clock without interruptions and to pay for the service whether or not you can use 100% of its capacity that day.
If I want to start a shipping business I can talk to an import/export broker and work out a schedule, where regardless of my circumstances I will ship 1 container every 2 days with him on a clock and because of that certainty of payment he will give me a much better price than he could anybody else.
As to Rockefeller's 'secret deal to prevent shipping for others' - baloney. The so called 'secret deal' was no such thing, it was a discount that Rockefeller was getting that nobody else could get because they would not ship a supply of that much oil on the clock, whether they have it or not that time and pay for a prearranged amount of delivery as promised.
Rockefeller was absolutely right and the reason that oil never went below 7 cents was exactly because government destroyed his company and did not allow him to find new ways to increase demand by lowering prices even further. Nobody was finding any better way of doing business in that time, otherwise they would have won against Rockefeller and that is all there is to it.
Microsoft had a temporary monopoly for a very good reason: they provided the computing platform that nobody else could provide at the price and just because you can't accept that doesn't change that fact. Microsoft and others also pushed hard enough in the market that competitors actually had to innovate to become competitive in that market, which is how free and open source software came to existence.
As to me being 'religious' about free market - I cannot stand hypocrisy of the modern society that will vilify the individual and promote the collective and use the force of the collective to oppress the individual. If I am 'religious' about anything that would be the belief that individual freedom tramps every so called 'societal good' that you can come up with that is based on lies, oppression, destruction of the individual, theft from the individual, slavery of the individual by the collective.