From what I understand, you're mostly right. Although I don't know enough about Internet infrastructure to speak definitively on the topic, I believe it's hugely expensive to run fiber cable for any meaningful distance. Any new competitor would have to run their own cable lines, and this creates a pretty high barrier to entry. It'd be like running another power source or water pipe network to your house, which is why the concept of Internet as a utility makes sense.
Another problem is that corporations either sue or lobby cities and states to prevent them from setting up municipal networks, in order to maintain their control of distribution. One major exception is Chattanooga, which built an excellent network and is now one of the fastest-growing cities in America. In many cases, cities can't do that due to lawsuits or regulations proposed by telecoms.
So here we are, with crony capitalist regulations on one hand and other regulations to help offset their impact on another. Only now the offsetting regulations are gone.