Barring the fact it's Disney, I figured all along the whole reason he agreed to Will is that besides Norrington, nobody else would have her. And this may be even before her abduction - Elizabeth is 20 years old and has only one prospect that her dad is pushing rather hard. Now I understand a commodore would be very successful, but honestly, if he had ties in London - as a politician would - the proper thing would've been to debut Elizabeth in London (staying with relatives or a trusted older female chaperone) to seek a husband. The fact he can't seem to marry her off - or she won't BE married off - suggests that despite all evidence we see to the contrary, Elizabeth's really more trouble than she's worth from an average society bachelor's POV.