According to this ted talk[1] he wasn’t. He led dangerously unprepared missions and ignored locals advice. Roald Admudsen was more successful and did it without the drama.
This business professor, selling his books on leadership in a Ted x (!) talk lost me when he called Amundson "forgotten". Like hell, no, Amundson is not at all forgotten. And Shackleton is famous for saving everyone on his doomed Endurance expedition under extreme circumstances.
Only measuring leadership, as im the Ted x(!) talk, with achievement of a stated, and up to then impossible, goals and ignoring a leader who saves everyone from death is at best short sighted, at worst ignorant. Did I mention the guy in the talk is a business professor with a book on leadership?
[1]: https://youtu.be/b0Z9IpTVfUg