The motive of maintaining reputation,avoiding a divorce and it's repurcussions among family and collegues,
maintaining control over the murdered spouse even though the murderer no longer feels the spouse is filling his or her needs ,
the narcissistic need for adoration of others and resentment over the possible or real loss of that.
Even a child or expected child can be a threat to the need for being the center of the universe...
If prosecution can convince the jury that Hacking operates as you (and SpottedOwl) have indicated, so much the better. It will strengthen the case for the most apparent motive being a motive for murder.