The change at that time alone was enough to cause a significant impact. After all, previously, the Allied Army of the two races had no morale to speak of. Hence, with their full strength only able to exert one or two tenths of their power, defeating the Burrow Spiders would have been very difficult for them at that time. But with the appearance of that change, while it's hard to say their morale will reach an astonishing height, it was at least enough to support their upcoming combat.
If initially the Allied Army of the two races had less than a fifty percent chance of winning the war against the Burrow Spiders, now, after the morale boost from previous events, they at least have a fifty percent chance of victory.
And as the situation unfolded, the morale of the Allied Army, no longer fearing the Burrow Spiders, naturally led to better performance in the ensuing battles.
