How are they monopolies? Competition is allowed. They choose to not compete in markets, either by not entering the market or buying up competitors. America used to have a stronger take on competition law, but for decades it's considered anti-business government regulation.
Google Fiber only launched in a handful of cities where the local bureaucracy had committed to bypassing many longstanding procedural barriers. They found laying new cables to be all but impossible everywhere else.
Do you think consistent campaign contributions to both parties, relentless industry lobbying and this all being perfectly legal may have something to do with it as well?
Speeds 10x that shouldn't even be an option in 2020 honestly. It's a failure of capitalism that they are.