Suppose a big breakthrough comes out of a private company, and such innovation is necessary to use nuclear fusion.
The company will be free to do whatever it pleases with the technology or it will somehow "force" to let other use, maybe behind the payment of some royalties.
Suppose a private company manages to lower the cost of electric energy by 90%, using a device self produced fast with virtually no capex. From an economics point of view, they build free money printing presses, essentially.
How would they benefit from this the most possible? Selling the energy? At what price? Take over sectors of the economy where electric price generates most added value? Aluminium production? Data centers? ...
Selling the energy mostly wouldn't make sense, since it means replacing regulated utilities. You could sell the reactors themselves but you'd have to be good at scaling up factories fast; unless that's a core competency you'll probably make money faster by licensing to people who are good at it. Or, just outsource the manufacturing.
Either way, if you can churn out lots of reactors fast, just sell them to everyone. Don't bother trying to take over e.g. aluminum production; what do you know about producing aluminum? How long will it take you to learn? Just sell the reactor to the aluminum producer.
The modern approach seems to be to just let people find a way around the patent, or simply ignore and litigate.
This only matters for the life of the patent, and is consistent with the intent of patents.