Allen is able to make guys miss and buy a second when he needs it so taking a guy out of coverage was an advantage to Allen in a big way. It also looked like teams figured out that even if their rush wasn't able to get to Allen quickly, that the Bills offense was more than happy to take that time to try for a big play downfield which then got them into a catch 22.
I don't know how much was Dorsey, Allen, zero threat to run the ball or the offensive line being bad, but they need to be able to make teams pay with the run and/or short passing game (and man did they seem super awkward on screens). The Bills offense was 1 dimensional and that is always easy to defend regardless of what that dimension is (it's a testament to Allen that he was still as good as he was and they scored as much as they did).