Not only was the first expedition defeated soundly, but their equipment also helped the defenders gain the first god in the history of the world. It was an epic failure on all counts.
That failure is another reason why the Yggdrasil civilization doesn't rely on only machines, guns, and an army of robots to invade a world. It is not the first time their equipment has been turned against them.
It is good to have a technological advantage, but it is not good to rely on it too much. According to Wrath, this mistake was why the first galactic human civilization was destroyed.
The most important technology of the first human galactic civilization turned on them, which led to their downfall. It has happened to the Yggdrasil many times since then.
