It's realistic
from that trailer, i can tell you it was not realistic, since middle aged fat guy who is probably impotent in a huge truck would likely not have the mental stamina to persevere stalking someone for several hours, tracking down her husband etc. I mean, that guy would get hungry and because of lack of metabolic flexibility his entire focus would shift to getting is next dose of donuts and hamburgers, that karen would just be a far away memory at that point