It's a prisoner's dilemma. Regulators have been made scared of the concept of having a part in making a different monopoly if they cripple the existing near monopolistic companies.
Who cares? They can just topple them again, every time one company grows too powerful. Just like mowing my lawn: I don’t complain that if I mow the grass, it’ll come back. I just mow it every time it grows too high.
It’s all part of the churn, and the government has abdicated their role of monopoly lawnmower.
