Hey there!
So sorry to hear about your husband and what you are going through. I didn't know your husband, but I did read a couple of his posts in which he explained he was depressed and had stopped taking his insulin. Several forum members offered him support and encouraged him to go to his doctor.
I'm afraid that you probably won't find the answers you need here, but I hope you will take some comfort in the support people offered your husband. Sometimes there are no answers. Depression is an illness that distorts the sufferer's perception, thoughts and feelings. It makes them act out of character. There is no logic to it. I hope in time you can stop searching for answers and come to terms with what has happened.
I hope you find some peace of mind.
Take care.
Smidge