It could also be that all teams had plenty of game tape of the Diggs Allen combo from the 1st year together and made a few adjustments.
We could also site the issues we had with the OL for the 1st half of the season...
Then there is Josh Allen, a player who most definitely is very happy and very comfortable Keeping Diggs here, and had some input.
Great WR"s have been known to stay very productive into their 30s. I see DIggs as one of those WR's.