Although the Hobgoblins Warlord immediately expressed submission upon seeing the Red Dragon, it was actually due to the overwhelming military power, sharp teeth and claws, and Flame Breath of the Red Dragon. If possible, he would have actually preferred to surrender to the weaker Green Dragon.
The foolish goblins, with lifespans of only a few or a dozen years, knew nothing and thought all Dragons were similar. But he knew, the Red Dragon was unpredictable; serving the Red Dragon required extreme caution.
Especially since they aren't as disorderly as the Orcs, they possess strategic thinking, but these strategies are likely completely unworkable under the Red Dragon, as it will probably just have everyone charge forward straightforwardly.
Leon did not know what the Hobgoblins Warlord was thinking, but even if he did, he could only smile helplessly.