Where's the Zimmer Whisperer?

This is a complete longshot but perhaps the promotion of Patterson to Asst Head Coach is to increase his visibility to other organizations for compensatory pick purposes. Since the Vikings won't be getting any compensatory picks in 2022 due to the free agents they signed, the only way they could add any extra picks next year (other than trading players) is through the NFL's 2020 Resolution JC-2A rule that states, "The employer-club of a minority employee who has been hired by another club as its Head Coach or Primary Football Executive (General Manager) shall receive Draft choice compensation in the form of a compensatory Draft pick in the third round in each of the next two Drafts for an employee hired as either a Head Coach or Primary Football Executive, or for the next three Drafts if it has two employees hired for both positions" (link).

If the Vikings have a really great season in 2021 and the defense returns to a Top 5 defense, it could be possible that Patterson is interviewed next offseason for a Head Coaching job. He is 60 and that's relatively old with the current trend to hire younger coaches, but the Texans hiring of David Culley, who's 65, is one example of a longtime position coach suddenly becoming an Asst HC (Culley was promoted by Baltimore to be Asst HC, Passing Game Coordinator and WR Coach in 2019-2020) and then getting a Head Coaching gig the following year. There are also 7 current Head Coaches in the NFL who are 60+ (Carroll, Belichick, Arians, Culley, Zimmer, Reid and Fangio) and a few more who are about to hit 60 (Rivera, Harbaugh & Gruden).

When the Lions hired Rams executive Brad Holmes as their GM, the Rams received a 3rd Rd compensatory pick in 2021 and will receive another in 2022. When the Jets hired former 49ers DC Robert Saleh to be their new Head Coach, the 49ers received a 3rd Rd compensatory pick in 2021 and will receive another in 2022. 

Head coaches on the hot seat entering 2021 that Patterson could theoretically go to: 

Kliff Kingsbury: if Kliff doesn't get Arizona to the playoff w/ an exciting rookie QB, his wings will be clipped
Matt Nagy: someone has to pay the price eventually for Mitch Trubisky; Nagy & GM Pace both might be unemployed after 2021
Jon Gruden: how much is enough?
Mike McCarthy: Jerry gave Mike a pass in 2020; not so much in 2021
Zac Taylor: in his 2 seasons the Bengals have gone 6-25-1