My best friend - let's call her Kate - left her partner - let's call him Ben - last year when she was 25 weeks pregnant with their third child. Ben had barely spoken to Kate for months. He had been distant from the DC too, and spending a great deal of time on his phone. He changed the password which Kate had known to fingerprint recognition, changed his FB so she couldn't see his friends or anything he liked or commented on. Ben began staying out all night regularly, under the guise of 'work.' He had previously been caught lying about porn use and said he had a porn/sex addiction. Kate was a SAHM and Ben was very very tight with money. Kate had no access to any of Ben's accounts; he'd transfer her money for groceries.
Kate tried talking to Ben to resolve things; the DC were unhappy when he was around and Ben seemed unhappy around them too. Kate asked how she could help and made suggestions to improve things. Ben kept promising to try but changed nothing. Things had been this way for a year or so; the pregnancy was unplanned. Kate decided that she didn't want to stay anymore as everyone was miserable and Ben wouldn't communicate. She was pretty sure he was being unfaithful and asked me if I'd lend her the deposit to move out, which I did.
When she had everything in order, she wrote a long letter to Ben explaining how she felt - that he'd been distant, secretive, financially abusive, disrespectful, ignoring her and the DC and that she had tried but he just wouldn't communicate and she couldn't take it anymore. She left the letter for him to read while she bought the DC to me so she could go back and talk to him. He didn't try and dissuade her from leaving at all. He asked where the house was and if he could help her move. He offered money for appliances. He didn't dispute or explain any of the issues she had written about and when I returned the DC he was more animated that we'd all seen him in months.
Over the following months he'd drop in to see the DC at their new home but still be firmly attached to his phone and very secretive about his whereabouts. He missed the birth of the baby as he didn't answer the phone or messages. Contact has now dwindled because he's finding it all too difficult 
Personally I think his not trying to stop Kate leaving and actively helping her do so reeks of guilty conscience. I think she was doing him a favour by ending things so he didn't have to be the bad guy and could instead play the heartbroken and abandoned card. What do you think?
And before you tell me to mind my own business, Kate is interested in outsiders opinions.