Matt - does it matter if it is MLC or not? Well, yes and no. 25yrs is right, and gives great advice. However, many years down the line it is important for me in my general sense of well being and this is why.
If it is marital breakdown, then we have contributed in some way. if it is true MLC then we haven't. Doesn't mean we were perfect or that we don't need to work on ourselves
It reminds me of an interview with Patrick Stewart (Star Trek) whose father used to physically abuse his mother. When the ambulance men came they would say 'Mrs Stewart, you MUST have done something' and he said firmly 'She did nothing'
When the LBS thinks it was something they did, or could have done differently that contributed, it is a different mind set from realising that we didn't 'do' anything to invite this (except have them in our lives). It happened regardless.
In a shorter, milder crisis, there may be things that the spouse can do, but in a full blown MLC all we can do is watch from afar as our formerly loving spouse turns (all too often) into a monster. Look at Wishing. There have been many over the years. It helped me to know that it was more than a WAS, that I didn't contribute. Just my 2c