Except usually sovereign wealth funds are for diversification, so oil rich nations will use their wealth fund to invest in non-oil linked commodities, since then if they're revenue dries up their investments shouldn't. Even better they can invest in this with an inverse correlation to oil such as green energy, so when their oil revenue dries up their investments go up.

Nvidia is not diversifying, but investing in it's customers, which are very very linked to it's own performance.