In modern society, if you need a rainy-day fund that still requires stashing cash, that's seriously outdated.
The wealth of the Tiren Formation isn't about finding a spot to dig a hole and hide cash, their method is very modern and convenient. They use an offshore company that has nothing to do with Ethiopia, but the company's account happens to have a $50 million cash flow lying in it, which can be transferred immediately whenever necessary.
The Tiren Formation has also received guidance from an expert, they have a trading company in the Bahamas, which has transferred $50 million to Gao Guang's shell company in the Cayman Islands, and with that, the deal was sealed.
Such a minor matter, clear to those who play with capital. It's all above board, hardly any tax to pay, and most importantly, a normal trade between two legal offshore companies, what's it got to do with the Tiren Formation, or with arms dealing?