I think he was tired of her. I think they had initial attraction and had a baby while that attraction lasted, but they were not suited for one another long term - but she was trying to make a family somehow work. But he wasn't into her (imo). My hunch is she was too successful and perhaps too straight-laced (not sure the right word....but didn't fit in with his good ol' boy lifestyle).
I just don't he was interested in what she was interested in, and perhaps she didn't fit in with his life (and maybe he had his eye on someone who did), and rather be stuck with a lifetime of a mismatch, he got rid of her. Speculation only.
THANK GOODNESS he wasn't equally disinterested with the baby.
RIP, Kelsey.
jmo