Innovation gives you a valuable competitive advantage - that doesn’t mean it lasts forever - that’s why companies have to constantly develop to stay competitive.

Or, they gain enough power to create a failed market, in which it is practically impossible for new entrants to compete and eliminate the incumbent’s rent-seeking. This is what we so often see now, particular in markets with strong economies of scale.

An “efficient market” does not mean it is at its optimal efficiency all the time, but that there is an efficient equilibrium it is capable of tending towards.