This is inevitable, when you've make the decision to keep a flawed law in place. These insurance companies have set premiums and benefits based on a market distorted by the ACA's requirements. They employ thousands, and provide insurance protection to millions of Americans, including in lines wholly unrelated to health insurance.
Everyone knew the old system needed propping up. One solution was to get rid of the system. That was never done, indeed all that was done was to kick out one of its key supports.
This is the sausagemaking that is public policy. It's like when the doc prescribes a drug to address your malady, and then a second drug to counteract the destructive side effect of the first drug.
Yes, the system is messed up, and conservatives tried to kill it. But they found out, for better or worse, they didn't have the political clout to do so. Inconvenient truth - more Americans want to treat the patient than kill it. And so the current Congress is tasked with managing the decline.
And it is going to cost money.