The status quo doesn’t benefit people with money. That they don’t get a significant benefit from Medicare doesn’t mean that shitty insurance somehow benefits them more.
Most of these companies are public, and you do not have to be rich to own shares. Also, tons of rich people do not own healthcare insurer interests. Tbh, they generally don't perform exceptionally well.
"Rich people," as a group, do not somehow benefit significantly from insurance companies being garbage to those they insure.
Edit: I think we should do something about it, but money = speech so there's nothing to be done as long as the status quo benefits people with money.