Mountains are often connected with great sages. The place that one must ascend to ask their wisdom. I first came to the understanding that the mountain was the challenge that one must overcome to seek wisdom. Then, I came to realize that the sage was the first to struggle to reach the top of that mountain.
Recently I began to question this connection deeper. As you move closer to Tao, you begin seeing the deeper connections of the world and become part of the greater whole. I assumed this meant that ascending the mountain was to become more in touch with nature, away from the distractions of society. Therefore, the one to climb the mountain for wisdom will see that all their struggles amongst people are for naught as all that is perfect is provided by nature.
I came to a new possibility as well. Maybe... just maybe. The sage was tired of how blind the people were to their actions, how deaf they were to wisdom, and how vocal they were about their so called entitlement; so he left to somewhere peaceful. And the one that climbed that mountain... proves that not the entire world is worth turning away from.