Even without knowing much about the ISP business it seems clear that simply removing net neutrality is not going to improve competition. Established companies do not push for changes that increase competition.
What is needed are regulations that mandate sharing of network infrastructure. That would create healthy competition. It’s working in South Korea, the country with the fastest internet.
And no, we do not know what the market will produce will be better than government regulation. All that we do know is that a pseudo-monopolistic industry will get to operate with fewer regulations. And it will behave like any other unregulated monopoly, which is poor service and high prices – i.e. the same only more.