Turning to the bush

The pasuk describes Moshe's encounter with the burning bush.
And Moshe said 'I will turn now to see this great sight, why is the bush not burning. And Hashem saw that he turned to see, and G-d called to him...'

The clear implication is that G-d only spoke to him when, and because he turned to see the bush. Why was that so great an act?
Moshe exhibited with this a tremendous desire to learn. He appreciated the greatness of the supernatural occurrence he was experiencing "HaMareh haGadol - This great vision", and wanted to understand it.

But it was more than that. The Medrash describes the setting under which Moshe found himself by the bush. "Moshe had gone to the desert to prevent his flock from grazing on private grass. One sheep broke away, and Moshe chased it till it collapsed from exhaustion in front of Har Sinai. Moshe lifted it to bring it back to the flock, but then saw the vision of the Bush. Hashem had said, in essence, that he who cares enough about the individual lamb would care enough about His people."

So, when Moshe turned to the bush, what happened to the sheep?
Moshe could have decided to bring the sheep back and return afterwards to investigate the "fire". Just dropping the sheep after all his efforts to get it must have been quite frustrating.
But Moshe understood that "tomorrow" doesn't always arrive. He had a once in a lifetime opportunity to see a fire such as this, and he wasn't about to let that chance slip through his fingers. This quality of recognizing the value of NOW is vital for a leader.
Lastly, Moshe was willing to re-prioritize. A minute before, he had only one goal, that of saving his livestock. Mid step, he was willing to rethink if that was really the ideal action. Deciding that his personal growth was more important (he could buy Yisro another animal) he abandoned his original goal entirely. How much is lost due to "well, its a waste of time, but I'm so close to the end..."?

R' B. M. Ezrachi, Rosh Yeshivah of Ateret, once said "a great man is one for whom every action is a great action". Someone who is constantly judging the value of his actions and reprising what his priorities should be and how to achieve them, considers every action important. He is the one who would drop everything to learn from the bush. And he is the one Hashem would choose to lead Klal Yisroel out of Egypt.