I agree a rule of thumb is that people don't do crimes that hurt themselves, but just because it looks like the suspect would get hurt does not mean the possibility of a plot is debunked. Just for fun here is a mildly plausible scenario that could includes all three of your examples without affecting the rich.

1. Create horrible apocalyptic virus that gives the victims fatal cancer.
2. Create vaccine. (or alternatively the cure for cancer and only use it to save the elite in ways that would not be obvious. Let some die..or give less than fully effective doses so the chemotherapy can be blamed for the improvement. This strategy was used in WWII when allies only fully or partially saved some convoys despite knowing of every german encrypted attack order)
3. Wait for war that can not be won conventionally.
4. Use planes to spray the populations of all nations on your side of the war. Double check anyone important gets the vaccine. (I doubt any vaccine though can be effective delivered this way but...sake of argument I guess)
5. Release virus to win war.