I am in a limbo here but let us wait for the official conclusions. Rush made one big mistake during this voyage, and this is what i hold against him, but I can't call him a grifter.
To be frank, any expeditionary-type discovery is probably made by the same type of people, and led by the same type of people. We consider Captain Scott a hero, well aware that he was driven by ambition, financial circumstances and yearning for the fame of being the first. To add, he had an obstinate character and was later accused of poor planning as well. Still, a hero.
Take Roald Amundsen, his nemesis. His memory about an explorer's book:
"I read them with a fervid fascination which has shaped the whole course of my life".
This "fervid fascination" is probably what describes all such characters, including Rush. Amundsen was not always straightforward about his goals. He planned his Antarctic expedition better than most, probably due to his experience from living with the Inuits. But, he died as he lived, and it, too, was for fame. Legends were told about his abrasive and competitive nature.
Perhaps it is is best described here. (I read Nobile's memoirs too, so, in general, close).
The conquest of the North Pole was highly contested in the 1920s. Arguments, insults and mishaps were part of the daily routine.
polarjournal.ch
In short, if I were asked to guess if Rush were driven by the money or the fame + "fervid fascination", I'd say, the latter. I wouldn't be surprised if he invested way more into these endeavors. Ambitious, obstinate, overly relying on himself to the degree that he ended up dying himself and taking four other people with him - doesn't it sound familiar? Weren't most of the famed explorers the same?
Over centuries, how many of them died, ruined ships, airplanes and took others with them? But then one would achieve, return back, and the mankind would discover the New World, or get a better map of the Earth.
So this is what I think of it today. It's the type we are dealing with. And all their constructions were often held together with spit because of financial constraints. Today, the materials are more flimsy, the trend is towards lightweight, and the obvious is seen sooner.