they werent playing "prevent" defense. they rushed 4 for every play but the last one, and the vikings beat them on each play.
the vikings decided to play into the lions' hands (paws?) by running the ball all the time. every time they threw to jefferson, he was open. but they decided to run the ball continually instead because that's how mike zimmer coaches.
they just got beat. it wasnt because they rushed 3 or 4 or 2. its because the vikings had the ball last and made a play. it happens in the nfl continually, every week.