I think that the insurance was a back-up plan, so to speak.
GG sees women as something to use, they are simply objects to him and he exploits them to get something he wants out of them. Plus, in my opinion he is a sociopath and has a sense of entitlement beyond a normal person's comprehension.
GG also knows from experience that a lot of women refuse to go along with his desires and don't give him what he wants. So, just my theory, he got into the practice of purchasing the insurance policies in order to insure that he always gets what he wants.
That is, if it doesn't pan out the way he planned with a particular woman, he has the insurance as, well, as insurance. Now, surely he knows he can't do this repeatedly and get away with it. Yet, as far as we know he has not gone through with it until now.?
What we do know is that GG has a history of extreme issues with women, and we also know that he had ongoing financial problems.
Not saying that he is a serial killer, but I believe he is a sociopath without a true conscience. So I don't find it a stretch to believe he could pull off a murder, especially if he became enraged at the woman denying him what he believed he "deserved".
We at least know from his history, that women are only things to fulfill his wants and desires. And I think that sense of entitlement to get everything that he "deserves" is what motivates him completely. :twocents: