The King and Queen Dragons have an unspoken rule. Due to their overwhelming pride, it is not an everyday scene you can see them asking for help nor stepping up to assist the fighting one. Once you take a bite, it is a Dragon's task to chew it and finish the battle no matter the outcome.
This is more especially to those who are at the higher ranks.
The previous collaborative attacks were an agreed tactic first suggested by Leah the Queen Dragon of the North and helplessly agreed by the rest of the King Dragons provided they will stick to the plan.
But the sudden rolling attack initiated by Arthur, the current King Dragon of the West, was not a part of their collaboration. Clearly it was an attempt to try and grab the trophy for himself knowing that Elric had spent quite enough of his energy trying to survive their last combined attack.
