Insurance companies hold tremendous leverage over care providers, up to and including the power to effectively put them out of business on a whim. Care providers don't like picking fights with insurance companies.
The total industry wide profit numbers aren't relevant at all if you're running a small clinic going up against an insurance provider. Heck even if a single clinic made more money than an insurance provider, it would barely matter - the insurance providers have the power to stop covering your practice and kill it, a clinic does not have any such power over insurance providers.
There are 5 or 6 big insurance companies, maybe 2000 if we count all of the small ones and 400K medical practices. So even by this very simple money=leverage argument, each individual practice has far less money than the insurance company they are dealing with. So if more money = more leverage then these same numbers prove the opposite claim.
So its probably fair to say that the picture isn't as simple as money=leverage.
If a medical practice and an insurance company get into a dispute and one of them decides to not work together, the practice loses say 1/5th-1/10th of its customers, the insurance company loses 1/100000th of its revenue. I call that leverage.