You left out the dog and you forget that at first most everyone looked at it and guessed carbon monoxide poisoning, which was a pretty reasonable guess with the first small list of details.
And they were all very wrong.☺
Btw, they would have known almost immediately there was no obvious foul play involving the dog either. ie, no signs and physical trauma, injuries etc. I was pretty confident from the beginning this was not a who done it.
BTW, it’s also not uncommon with the elderly, long married folk, when one goes the other takes their own life. Very sad but not uncommon.