1. Was Shackleton a leader or an entrepreneur? How effective was he?
During his entire life Shackleton has displayed an amazing mix of abilities that belong both to leaders and entrepreneurs. Nowadays, we may fail to see that behind a leader there are many people working for him or for his vision. One may call these people entrepreneurs. They are able to perform difficult task starting from scratch, but they usually lack a vision of their own, or at least they lack a vision that addresses more than their own person.
Shackleton, on the other hand, had to perform ask assimilated to both being a leader and an entrepreneur. Putting in balance all these things, it seems to me that Shackleton was a leader, who had to do the work of an entrepreneur in order to achieve his vision.
I consider that Shackleton was effective in both his endeavors, as an entrepreneur and as a leader. He succeeded in organizing the expedition (logistic wise) as an entrepreneur, he succeeded in selling his vision to Maecenas for obtaining funding as a leader, he personally led the expedition in its minor details as an entrepreneur, he empowered his men to survive the ordeal as a leader, and he was reckless in following a crazy and dangerous vision, just as a leader.
As a conclusion, I think that while Shackleton was successful in both positions, he truly was a leader, backed by a very successful entrepreneur, all in the same person.
2. What were the underlying causes of the Endurance crisis?
Actually, the Endurance expedition was a disaster waiting to happen. Even though they used the top of the line materiel of their era, it is clear that they were severely under-equipped for what they were facing. Any expedition to one of the Poles during that time was actually tempting the fate and the participants were aware of the dangers that were lying ahead of them.
I do not think that anyone can be blamed on the disaster of the expedition, as no obvious mistakes were done