and sorry, i misremembered the numbers. he got over $400 million (at least) from dad, and that would be worth about $2 billion if simply invested in an index fund (according to the article).
https://www.bloomberg.com/opinion/articles/2015-09-03/should... is a good critique of these kinds of calculations in general - they usually assume perfect market timing
the trump wealth transfer started over 60 years ago. over the long run, market timing doesn't matter that much.
(EDIT: and that opinion piece was not coherent; the author mixed up trump's businesses with his net worth, and convoluted other finance concepts to render his desired "opinion". it was awful.)
Besides, there's no claim that he was given anywhere close to $400M over 60 years ago, nor can anyone be realistically expected to invest their inheritance starting at the age of 12.