I don't think there's a "there" there.
I think a lot of football fans do this to manage expectations and emotions. It's really fun when your team comes into a season not expected to do all that much and then proves everyone wrong. It's not fun when your team has high expectations from everyone--and then proves everyone wrong.
So I don't think fans really believe that high rankings cause their team to underperform--but when you're ranked really high, anything but living up to those rankings is a disappointment.
This.
When I was in school, the first team I watched had modest expectations and exceeded them. There was a good start followed by some slips, a rise that was a bit of a mirage, and then a bowl upset win. The next year's team again had humble beginnings and did well against a soft schedule with a young team.
The next year was supposed to be THE year. A few seniors were gone, but only one was being replaced by someone who wasn't more capital T talented. That was the year the program would take a step forward, contend for the conference again, make a big run. The rankings were high. But then the start was slow it took a while to get the first loss, but it was one that stung. It turned out, the senior experience mattered a lot more than I understood. By the end, a perfectly reasonable season had been fraught. I can't watch certain players from the team without some disappointment, and that's not really fair.
The next year was similar. Expectations were a little less, but the group was very veteran. The next great savior was coming at QB (this is where I learned about transfer expectations). The backfield was loaded, the best pass catcher back. But the start was similar to the year before and then the bottom fell out. The team was a titanic disappointment.
And then the next year, the expectations were modest again. The team lost to the two best teams on the schedule, slipped up against a solid foe on the road, pulled an upset in the bowl. And I was reminded how pleasing it is to not get out over one's skis and have to talk it back all season.
I think less about rankings and expectations now than I did. Even as two of UW's best pass catchers are embroiled in something both terrible and probably stupid on their parts, I'm not too worked up. But I think back to that and always like starting a little lower, just so I don't have to talk about what's going wrong early on.