A Random Scrub that burn stunk, but his donphan wouldve been at 25%, which is easy ko range of crobats BB or hydreigons dp, so no it didnt matter even with the burn.
As for the missed zen headbutt, it was on chandy not crobat. At that point hydreigon wouldve just came in spammed dp or u turn. That P2 mustve been neutral natured and 252 ATK EVS
+1 252 Atk Porygon2 Zen Headbutt vs. 112 HP / 0 Def Chandelure: 103-122 (35.6 - 42.2%) -- guaranteed 3HKO
It did 38% as you saw in the replay, so thats most likely the spread.
He may have caughr me off guard, but it didnt make a difference at all since he had nothing fast to check hydre and crobat with the exception of bp on guts champ. Plus who runs supporting chestorest kingdra??