If a spouse takes the time to look under every rock, informs their spouse about their concerns, initiates marriage counseling, communicates, makes a pros and cons list and treats their spouse with respect as they make their decision being honest, then you don't have a 'walk away spouse'. If the spouse is approaches it maturely, takes accountability for their contribution for the erosion of the marriage and is aware of all the consequences, their spouse part of the process and after doing the 'work' realize that divorce is the outcome, then it becomes consensual.
When the departure is abrupt, the spouse is involved in an affair and/or places all the blame on their spouse then it's a one sided decision and not respectful of their partner.
Are the spouses who leave 'bad' people? No, but their actions are irresponsible. And those left in the lurch are not perfect either. Our saving grace in being at this site is that we work on growth, awareness, culpability, honesty in our actions and communication skills which were probably lacking with our spouse.
My former spouse decided within two months of 'dating' a woman during the marriage that he was miserable and was 'done'. He promptly moved in with her (secretly) and eventually married her less than four months after the divorce was final. He lives by her rules. Do I respect the manner in which he made his choices? Absolutely not. Do I accept that I was in a one sided relationship rather than a marriage between two loving partners? Finally.
It's hard to let go of the fantasy to accept the reality and face the fears of being divorced. No one is flawless. It's how we get up from this shocking experience that defines who were are.. in the now, the present, not the past.