Just invest 20 billion, get 20 billion back on its own isn't inherently a problem. The issue is it may inflate the figures and valuation for NVIDIA such that it collapses when the boom ends. If their sales rely on handing loss making companies like OpenAI money to buy their products then that may fall apart if things turn. Cisco did similar in the dotcom boom and bust. On the other hand if OpenAI doesn't collapse then the investment goes up and everyone wins. It's kind of a gamble on that sort of thing.