"...Major General Lu, the situation over there is quite terrible. Our National Defense Strategy Department and Department of Religion (the department that communicates with the Proper God) have investigated and used divination, and feel that you are the most suitable rescuer."
Although "divination" may feel somewhat peculiar, in this era, results obtained through extraordinary traits and spiritual intuition are often more effective than precise calculations.
As for Lu Ping'an's abilities... he indeed is a strategic level asset who can influence the whole Plane War significantly as a major strategic chess piece.
Lu Ping'an did not respond directly; being referred to as "Major General" also hints that this commission might be an official expectation.
In some sense, this general rank was a favor that Lu Ping'an owed.
At that time, they gave him an honorary rank that's typically reserved for eighth-tier, which was a clear demonstration of the official stance to protect him.