The Steelers controlled the AFC North for 15 weeks with the Ravens, Browns, and Bengals all losing off the bat. From Week 2 through Week 16, they dictated the fate of the division. And they squandered it, doing so in spectacular fashion. They lost their final four games, and the Ravens won their final four.
That is what needed to happen for the Ravens to pass the Steelers for the AFC North. Or close enough, anyway—the Steelers could have won last week and still lost the division. But the point is, they had the Ravens where they wanted them all along, and let them go.