There have to have been passengers who were watching the time, due to connecting flights and business or personal appointments at the destination. I’m guessing the flight attendants were totally out of it too, distracted like the pilots by some activity they weren’t supposed to have been engaged in, and were roused into knocking on the cockpit door and rousing the pilots by a passenger inquiring as to when the heck they were going to be landing, seeing as how they were still heading straight at full altitude at least 45 minutes past the point where they should have begun descent, and there had been no announcement of a delay or diversion.
I agree, many passengers must have noticed and started asking questions, I sure would have. Much less fly past MSP, no chance that gets un-noticed.