The nation that left Egypt was not the same nation as the one that emerged from the desert. Although they were equal in numbers, the people who entered the desert were fiery individuals, whereas the ones who were about to conquer the Promised Land were subdued, compliant and accepting.
Man was created to participate in the completion of the world, but the time had come for a different form of participation, a more passive one: The desert generation were all leaders, men who had their opinions about how things should be and were not afraid to voice them even to the emissary of Hashem. The ones leaving the desert on the other hand were ready to respond to the 'order of the day': two prescribed sacrifices on weekdays, an additional one on Shabbos, etc.
Responding can also be a form of action, and is the conduct that typifies Malchus, the 'feminine' Sefira. As they were each about to inherit their part of the Holy Land they had to first internalize it's nature, the nature of reciprocity: receiving and giving. The earth receives seeds and grows them into plants, it does not decide which plants to grow; so the people learned to serve Hashem according to His dictates, developing them only in so far as they were extensions of His command: this is the secret of the Oral Torah.
Just as Moshe was compared to a sun that radiates energy, so Yehoshua and the people he led were analogous to the moon that receives light and reflects it in different directions and shapes depending on its relative location. The time had come for Moshe Rabbeinu, the eternal leader who will soon lead us in greeting Mashiach Tzidkenu, to give over the reins of leadership first to Pinchas, whose primary motivation was emotion rather than intellect, and then to his disciple Yehoshua.
The male element of that generation hence all perished except Yehoshua and Caleb, and the women survived, for they did not participate in the Golden Calf. When the daughters of Tzlophchad came to Moshe for a judicial ruling he did not rule on his own based on what he had received, as was his practice, but passed it on to Hashem to rule instead; his time had come and a new period was about to begin.
Based on Rabbi Vali's book on Bamidbar. Questions and subscriptions can be mailed to: the Yeshiva