They were going it alone. There was no one else willing to take any risk with Zimbabwe. They didn't have any "sugar daddies" like we have with China, Japan, Germany, and Britain buying our debt. Even if none of those theoretical corn fields of yours burned, the same thing would have happened only not as quickly.
No fiat currency has ever survived in the history of the world. Don't you know that? Why do you embrace an abject failure used only as a means for the elites to enslave the world?