Taking prescribed doses of T for the purpose of transitioning is not "substance abuse".

If getting prescriptions is easy, you can abuse prescribed meds. It's a common issue. Hormones have been prescribed incredibly easily.

Again, T requires a prescription.

Again, look at opiates, valium or xanax, or various kinds of methamphetamines.

But if they are doing HRT they would have low testosterone. Which proves testosterone did not cause this man's violence.

Males get regular testosterone every day for their entire lives. They don't get sudden injections once a month, but their bodies have been built out of it since they were little boys, and even more so after they hit puberty. Even most men who have replaced T with estrogen still have higher testosterone than women just due to what their body naturally produces, but even if they didn't they have the lasting effects of what was already made.

There are cis women who commit violent acts, as well as cis men. Why did this case stand out?

I don't think people are saying this case stands out against some other case of a non-medicated woman attacking a woman, but just that in this case, a woman who is being violent should not be prescribed testosterone. This is a bad treatment plan. I would not think someone would encourage an abusive "cis man" to take steroids either. Rage and violence are well known potential side effects so if they seem to be manifesting, the prescription should be reconsidered even if your position is that the drug can be beneficial.