The replay isn't staged; it's taken from a real online game. The player controlling the Barbarians simply knew how dangerous Wingael's troops were (they can move first and decimate the enemy's army) and took some countermeasures. P.S. If you're interested in the theme of "Elves under the command of a non-native hero," try using a Demon as the leader (Necromancers aren't very promising due to their low attack stat and the low chance of getting the "Leadership" skill) or, at worst, a Warlock (even a Barbarian would be better than a Necromancer). ;)
Auto-translated