Regarding Washington doing better with the Seahawks in town relative to how the Gophers have done with the Vikings in town, the key is that the Huskies got really good just as the Seahawks were formed. Don James took over in 1975. The Seattle Seahawks had their inaugural season in 1976. Washington won the Rose Bowl in 1977. That 1977 season started a run of 16 seasons through 1992 in which Washington made 14 bowl games, including 6 Rose Bowls with 4 wins, and one shared National Championship. By comparison, the Seahawks had 4 playoff appearances in that same 16 season span, all concentrated in a 5 season span. They won 1 AFC West title and had 7 losing seasons with only 2 double digit win seasons in that run.
The following comedown era for the Huskies was gradual and coincided with average to bad Seahawks teams and an aborted attempted move to Los Angeles (the NFL put the brakes on that one) that badly alienated the fans for a few years. When the Seahawks started their big leap in 2003, the Huskies got really bad at the same time, but had banked enough good will and hardcore fans to withstand it and made some big facilities upgrades. By comparison, the Gophers started to badly fall off just as the Vikes rose to dominance. The last Big Ten title was in 1967. The Vikes won their first division title in 1968, were in the Super Bowl by 1969, and then had their great teams in the 1970s while the Gophers slid further from view apart from a few outlier seasons.
One thing that harmed the Gophers was that the Big Ten and what is now the PAC-12 had a deal with the Rose Bowl to only send a representative to that game and no other teams to any other bowls. This agreement lasted through the 1974 season. The need for bowl revenue among the member schools and some outstanding Ohio State and Michigan teams being home for the holidays during the Woody vs. Bo era led to teams going to bowls other than the Rose Bowl beginning with the 1975 seasons. This is important because the Gophers would probably have gone to bowls, even though there were far fewer back then, in 1962, 1967, and 1973, maybe 1968 as well. Going to bowls would have increased fan interest and perhaps rolled in a tide that could have helped with recruiting and led to improved teams in some of the non bowl seasons. By the time Big Ten teams could go to games other than the Rose Bowl, the rot of the previous decade had set in too deeply apart from the one off game in 1977 and the Holtz/Gutey year one bounce.