Looked to me like a combination of factors.
JW was playing really, really well - he's a streaky QB (as is Dalton) and he was on fire yesterday. Multiple third down completions where the he threw it exactly at the right time to the exact right spot, with the Bills' defenders within a half-step of him.
Losing Gaines hurt - JW ate the replacements (Johnson & Wright) for lunch.
Two dropped INTs (Hyde, Gaines).
The pass rush needs help - imagine how could the D would be with another top-end pass rusher to compliment Hughes.
Kyle is either injured or has lost some of his explosiveness.
LoRax is really struggling in pass defense right now.