The classical answer would be RCA, who famously bought Carpetland, Banquet Foods, and Hertz car rental, and was bequeathed the moniker "Rugs, Chickens, and Automobiles" by the investment community.

Buying a stake in Nokia is admittedly different than taking it over and managing it, but the danger there is very clear. Distracted management that strays away from core competence can easily kill the golden goose driving revenue.

The contrarian view is that Berkshire Hathaway is able to hold an array of successful manufacturing and service businesses (Kirby vacuum cleaners, Dairy Queen, Clayton Homes, and the prominent Sees Candy) without losing management control of GEICO and their other insurance holdings.

Hopefully, Nvidia sees the example of RCA and Gulf Western, and will not lose focus on their core competence.

RCA famously birthed the semiconductor industry in Taiwan. I think that focused trade regulation would prevent a repeat of that event in modern times.

Edit: It appears that RCA bought Coronet Carpets, not Carpetland.