You are jumping to conclusions here.
It is possible that UH took on insurance cases that included sick or vulnerable people that other insurance companies wouldn't touch.
It's also possible that their premiums were very low, so the poorest and therefore most vulnerable people were those that signed up. The policies themselves may not have covered everything that they were expected to cover, I'm sure there's a lot of fine print to go over that went unnoticed.
In other words, you get what you pay for.
I wouldn't be surprised that the insurers with expensive policies pay out a lot more than those with cheap polices.
BTW I am not condoning their practices or the system, it's a **** system we all know that, just looking at a wider perspective.