Mcdonald's famously invested in Chipotle as a risk mitigation strategy. If consumers want healthier fast food, sales at Mcdonald's will go down, and sales at Chipotle will go up. Investing in something anti-correlated with your business lowers risk by paying you when your own business is hurt by a surprise.

If you can see the future, by all means invest in the one stock that will go up the most. If you can't see the future, diversifying into assets that have negative correlation (one goes up if the other goes down) lowers volatility at the cost of limiting possible upside.

Nvidia has a massive pile of money. Where should they invest? If they believe in what OpenAI is doing, investing in it makes sense no matter what hardware OpenAI chooses. If OpenAI manages to make something much better than Nvidia hardware, Nvidia's sales will go down as the value of OpenAI goes (way) up. If OpenAI fails to make something as good as Nvidia hardware, they buy Nvidia hardware.

It is odd how internet commentators seem to think that companies make investment decisions as a way to root for a team. They do not. That is not how finance professionals think!