Do you know what's more powerful than entire military??
Logistic and Economy
Army without food and equipment,, cannot march, let alone fight
This MC isn't OP as if able to wipe out half battalion alone,,
but OP on knowledge, experience and more importantly, Trustworthy.
As working young adult, i can get why Demon Lord choose him to be one of Heavenly General, not advisor nor minister, but straight Heavenly General.
1 heavenly general can lead an army to invade a city,, but MC can lead entire nation economic and entire militarily logistic.
The position alone give MC enough relation, influence, power, respect and importantly, freedom to extent degree.
In newer chapter, Author give a glimpse what happen if economic held by wrong person, the pig merchant.
Imagine that happen during wartime.
That pig merchant will become or create liability even fatal weakness for Demon Nation.