Why my father verbally attacks me?

I’m 27 years old and I put myself through college I paid my own college. I got myself a decent job. I bought my own car and manage to pay my bills on time. Yet, my father when I talk to him he tells me I’m an idiot and don’t know squat for my age? He never went to college and worked at a warehouse his whole life. I truly don’t think I know it all but I have put in some effort in my life. I have at least tried. I have even managed to date someone who is working on her PhD. What is his deal?