Is it possible for them to have other strategic incentives for their action, such as preventing a type of competitor from emerging? Yes. And if you take the perspective that government is a uniquely troublesome competitor, it's understandable to feel extra strong about it.

But it's still monopolistic in context. A counterpoint to "competition from the government is uniquely unfair" is "having only one provider is uniquely unfair". One is from the perspective of a profitable $100B corporation, the other is from the perspective of the consumers.

The city wanted to launch a municipal internet service. Predictably, it failed because the requirements were to provide service everywhere and the bids all came back too high.

Meanwhile they continue to resist private ISPs who want to expand into neighborhoods where they think they can do so profitably.