Is this murder? No.

Plainly, yes, it is. Every knowingly illegitimate denial resulting in death from delay or cancellation of treatment is a case of the insurance company murdering a human being.

You really seem to be pulling the blinders on on this topic. Voluntarily choosing an action that one knows will result in another's death, even if behind bureaucratic abstraction, is more. Saying otherwise is almost literally the same as the fascists like Musk who claim that, since he didn't personally kill anyone, Hitler was innocent of any of the atrocities that the Nazis committed in WW2.

If the treatments were covered then the patient should continue to get care despite a denied claim and should appeal the denied claim, and in the case of delayed care they should sue the insurer.

Ideally, yes. In the real world, people who are undergoing chemo or other treatments for diseases that are fatal without treatment generally do not have the capacity to get a lawyer or file a lawsuit, between bouts of vomiting and unconsciousness. Even if the denial is overturned, delay in necessary treatment caused by the denial can, and does, result in the disease progressing to a point where mortality is guaranteed.

The former CEO literally preyed upon some of the most vulnerable people there are in the country to increase shareholder profits. He chose company policies and actions that he knew were illegitimate and would lead to people suffering and dying. He got better than he deserved.