Currently, I'm presented with two views on the purpose of sending spies - some commentators say that the purpose was strictly military (to learn the strategy), and some say to probe the land's resources.
It seems that both contradict the already established premises, by G-d and Moses and make Moses' approval questionable and surely provoke G-d's rage:
If the purpose was strategic, that contradict G-d's promise of "ה' יִלָּחֵם לָכֶם וְאַתֶּם תַּחֲרִישׁוּן" (Ex 14,14). They should have trusted this attitude as it worked already a couple of times. So, seemingly, Moses couldn't favor this idea. (see Malbim, for example, that they were not supposed to touch their enemies at all.)
If the purpose was to probe the quality of the land, that would contradict G-d (and Moses') promise that the land is good. So that way could also be interpreted as mistrust.
How do the interpreters solve those contradictions?
Rav Hirsch says that the initial request was (as I say in Did G-d command or not on sending the spies?) presented in order to follow the idea that the Bnai Yisrael would have to start living a normal life. This is based on the way Rav Hirsch explains לחפור את הארץ.
Rav Hirsch also points out that they were to then to see which parts were most appropriate for each tribe to settle based on the various characteristics of the tribes and put the military aspect in the background.
By the order: ויתרו את הארץ the mission received a somewhat different
and extended task. It was no longer just to spy out the most suitable
way to conquer the land. That purpose was to be in the background, and
the task set was to learn to know the land itself as a base for national
development and the significant indication was given to consider it
from two points of view, as ארץ כנען אשר אני נתן לבני ישראל it is at
the present ארץ כנען, the land of a most degenerate nation, and it is
the land was given by Hashem to the Children of Israel for them to develop
in it a national life according to His revealed Will, the Torah.