Darn, Mir, If I did not know you better I could have sworn you hired a private detective and found and interviewed my ex-wife. That is exactly what she would say and it is so far from the truth as anything could be.
We really don't know enough to say for sure but I would bet it was her fault and not for failure to read the red flags. We don't know if she put on 70 pounds like a lot of good American wives, if she nagged him to death like a lot of wives, if she really took an interest in him, if sex was something that they used to do way back when. There are lots of marriages that survive and yes, it is possible she did nothing wrong but there is a better chance she did.
Regardless is it really a failure. If they had a lot of good years together maybe a couple of nice kids and it was their time to move their life to a new stage. I can recall one of my customers years ago. He had operated a good business for 16 years, fed his family, led a reasonably comfortable and happy life. We sat in his office and if I can recall correctly he was nearly in tears as he told me what a failure he was since his business was now in bankruptcy. Really was he a failure. Does that one moment of failure wipe out 16 years of success. Is life a journey or a destination? If it is a journey he is not a failure, the wife is not a failure. If it is a destination, don't we all end up with the same destination at the end and doesn't that mean there is no failure or success.