Honestly, it is pretty much the same as their faux relationship with OW.
The MLCer is unhappy with his/her life. Everything isn't going the way he/she would like. It can't be because of them! Oh NO! It HAS to be everyone else.
So they run away from their "old" lives and attempt to start over with a new life. New partner....heck...why not new kids? The old ones are so difficult! They aren't happy with the "new" me. They seem to be angry, hurt....difficult. I can start all over with everything NEW. I can do it RIGHT this time. The "new" kids seem happy to see me. (or maybe not...but he/she can try - right?)
The problem is.....the MLCer took the main cause of all the unhappiness in his/her life with him/her when they ran. The MLCer took himself! The old baggage is still there....it just takes TIME to rear its ugly head again.
I know it is difficult to watch. Imagine how difficult it is for our kids? One my my co-workers (a male LBS) will soon have his 16 year old daughter move in with him - as she can no longer stand living with her MLC Mom and her Mom's OM. She can't stand to watch her Mom dote over OM's young daughter. It hurts her. She feels replaced.
This is, unfortunately, very much script.
L