The speed of their adaptation to each other was much faster than most of the soldiers had expected. The angels in particular had not expected that the strange races around them would welcome them to their side so quickly. But that was the key here, they were already used to other races.
The dragonkin, elves, demi-humans, and humans were the main forces being brought with right now. They were united while they had left the remainder of dwarven machines and dwarves behind with the merfolk. That was already a radical spectrum when it came to race. The angels were just humans with wings in the bluntest sense even though they were different internally.