SP500 10 year annual return: 14.6%
UNH: 13.59% Elevance: 10.79% Cigna 9.42% Humana: 6.1% CVS: 0.55% Molina: 9.42% Centene: 0.9%
Or, the likelier explanation, is that health insurance prices are highly regulated and have to get their prices approved by a government official(s), and B) they don't have a lot of pricing power due to the competition and they are not colluding.