I'm finding now, reasons why:

I was unhappy:  I was emotionally disconnected,  I couldn't openly communicate my feelings to my wife.  I was completely unaware of myself.

I was relying on my wife to make to me happy:  I thought making her happy would make me happy, and instead, I drug her down by putting more pressure on her.

I had no boundaries:  I was controlling everything.  Completely paranoid of my wife and her abilities.  This is part of a bigger problem of my accountability.  Which I had none.  I thought I was justified and it was my duty to police.  It drove me nuts, I was guilted with worry and tired with the hard work of it.  I believed I was giving just as much as my wife, but I was suffocating her and making her feel inadequate.  She wasn't, not in the least: I owe everything to this woman for keeping it together.  But, she wasn't.  She was slowly dying inside.  I had been living in a dream world.

I had the wrong mindset:  I told myself I could love my wife and still go through with it.  It could happen and she would never know.  I didn't love this other person.  My life was with my wife and my children and nothing would ever change that.  I would forget it.

These are not excuses, what I did was wrong.  This is not my wife's fault.  It is 100% mine.  I caused and allowed it to happen.