That's how the NFL scheduling works. This year, the NFC North teams play the NFC west, and the AFC North.
There are 2 games every year that are decided by where teams finished the previous year. Since the Packers finished 3rd in the North, they play last year's third place team in the South, (Tampa) and the third place team from the East. (Cowboys)
The Vikes finished first, so they play the Panthers and Giants.