I found that the biggest thing that caused me and my wife to split up after I got sober was co-dependency issues. Even though my drinking caused a lot of strife in our relationship, there was an element to it that satisfied her desire to be the one in control. I was fine with that when drinking, but after some time sober I no longer needed to be "taken care of". Where before I didn't mind her making all of the decisions I now wanted an equal say in matters. This caused a lot of friction in the relationship and eventually caused its demise.
And to be fair I was already an alcoholic when we met, so I am sure I subconsciously sought out someone like her that would take care of me since I couldn't do it myself. After getting sober I was a different person but she hadn't changed.