I had the same thoughts as you did:
Statisticaly, Ex's make strong suspects. But as you noted, divorce was years ago, no children. A surgeon is going to have money for good lawyers and will have plenty of post marriage romance options- even with out being "Mr. Personality".
One of the victims reopened the old divorce proceedings, might of found assets that he concealed? Surely, an angry, but still objective thinking surgeon would respond with something like one of the following:
A. Ok, here is the full amount of "X" right now. But... you need sign this contract renouncing all future claims.
B. Take "X"- 50%. Or, I"ll fund a lawyer and drag this out for years. Yes- any recreational this or that usage that I find out about gets reported to the medical board. But... Please, come get your X-50% and I will just go back to my life.
But double murder?