The entire history of economics backs this up. The only instances of long-lasting monopolies are the result of government coercion. The instability of large, profitable businesses has both a solid theoretical foundation and an unending abundance of empirical data.
If you ever think you have found a single instance of monopoly lasting any significant length of time, look deeper - with absolute certainty there is a government gun backing it up.
If you ever think you have found a single instance of monopoly lasting any significant length of time, look deeper - with absolute certainty there is a government gun backing it up.