That is an excellent question! One, I had not yet considered. Like other catholic politicians, my guess is that with this bill, he hopes to distance himself from the stance of the Catholic Church; to demonstrate to his constituents that he is not a servant to the teachings of his church.
I usually assume that politicians are doing grotesquely wrong things based on rational calculations of political advantage. However, maybe it’s just personal: men in sinful relationships have a “need” for abortion.