Everything you described involved a technology shift. What about commodities, where monopolies really matter? I doubt someone will invent an iron2.0. Monopolies are far more destructive when their influence allows them to soak up resources and access to them.
Haven't you heard? It's all about carbon fiber now. Even during they hey days of iron, skill mini-mills started popping up all over, using new, much cheaper and more efficient, melting technology. Same iron, different way to process. And even when Big Iron did finally catch up and switch to the same technology, they still lost simply because they were too cumberson to control outputs, while the small mini-mills could start up production as soon as someone needed steel, and shut down immediately as soon as that need was filled. Just In Time production killed Big Iron, who ended up with a bunch of expensive but unneeded steel sitting around in its yards.
The only possible monopoly I can think of is land/real estate. But even then we still have a lot of open ocean, and if it comes to it, can dig underground.