Much of the physical and logical infrastructure was heavily subsidized or outright paid for with public funds. One could argue that it was never economically viable, but forced to appear that way.

Internet infrastructure is not unique in this respect.

The idea that markets optimizing for profitability naturally tackle hard problems requiring immense up-front costs is an attractive lie.

One can look at existing mesh networks and see that it is indeed possible to have infrastructure running without commercial interests. Guifi is probably the biggest and most successful example of this. Guifi is mostly volunteer driven but also have commercial actors operating on it, helping people getting setup to Guifi for a fee. So the infrastructure is open but it does have for-profit actors helping maintain and create new nodes too.