You've got to understand those teams give big efforts, particularly on the road. Lousy teams in the NFL are not severely outmanned, not like college mismatches. Teams with a .250 or worse winning percentage late in the season generally cover the spread on the road, like Oakland did easily today. That's one of my reliable systematic angles. The team is embarrassed and on the road it knows it needs a supreme effort to remain competitive. At home the weakest teams feel heat from the home fans, the crowd is generally pathetic, and there is a tendency to collapse. They fare much worse against expectation at home than on the road.
The Dolphins keep hosting teams coming off an embarrassing loss. That contributes to the top effort level from the road teams. Seattle, Baltimore and Oakland were all coming off double digit losses when Miami hosted them.
Besides, the Dolphins aren't good enough to take anything for granted. I'm still trying to figure out how it was possible Miami was favored by more than a touchdown two weeks in a row.
Good clutch win, a score or lose situation on that final drive, against a decent defense.