When Moshe sent the spies to visit Israel he sent twelve, one from each tribe. At the end of the forty years journey in the Wilderness, when Yehoshua sent spies for the same purpose, he sent only two. Why the difference?
It has been suggested that in the time of Moshe, in the beginning of the difficult journey, the tribes were not united. They were all vying for positions of recognition. There was competition between them. Hence Moshe would not be able to select two individuals who would be satisfactory to all the tribes.
Forty years later, after Moshe succeeded in unifying the people, and after a new generation grew up, it was natural for Yehoshua to be able to make his selection and no tribe would question his choice. The tribes respected each other and relied on one another.
When people are united it is much easier to accomplish one’s goal and the results are also better.