Driving behind vans

I’ve only had my license for about 6 months now, but the one thing I absolutely hate about driving is driving behind mini vans. Why does every single mini van I get behind seem like they don’t know how to drive. Like yesterday I was driving home and this mini van pulled out in front of me when I was doing 45, and then continued to do 25 in a place where I can’t pass, while swerving all over the lane, not even in the lane sometimes. Almost every van I get behind does this and it’s ridiculous.