Well, this might be a very unpopular opinion, but if generating wealth correlates to intelligence and ability, and these traits are transmissible to children (either genetically, or through practices that parents teach to their children, or through higher educational investment), then you would expect a positive correlation between ability and amount of parental wealth.
This above argument could easily be wrong, but assuming that inherited wealth reveals nothing about ability on average seems like a rather strong claim.
Whether it's fair that parents can try to give their children an advantage, of course, is a totally separate question.
He's a billionaire who has spent decades producing a return worse than if he'd just put the money he got from his dad in a fund. His fortune is not a demonstration of ability.
He's functionally rich, but we have no proof that he's really a billionaire. His finances are opaque. We don't know how indebted he is. We don't know what his revenues are. (Crain's reported a few months ago that Trump Org has historically overstated revenues by a factor of 10.)
This is speculation, and I personally don't find it to be true anymore. Funnily enough, I was on the opposite end of this argument as someone else on reddit about a year ago, when I cited an article from I think the daily beast, making the exact same point.
Among the flaws with the argument though, are an assumption that he could track the market (or that it would be a good idea), which is a flawed argument because Bogle didn't even start the first index until 1975, and until the 90's index funds had a reputation of being terrible. It was an undeserved reputation, but the idea of dumping hundreds of millions into an index was just unheard of.
Again, it's also an issue that there was no way to track the market prior, so what was he to do with the money from the age of 18-28? There's also the issue of the article I read assumes the absolute minimum value it could find for the value of Trump's brand.
While I think Trump valuing it in the billions is absurd, so is stickering it at $30 million, even before the election. It seems in bad faith to me to choose the weakest possible version of the thing you are arguing against, especially if that's the only possible way to make the math work out.
This above argument could easily be wrong, but assuming that inherited wealth reveals nothing about ability on average seems like a rather strong claim.
Whether it's fair that parents can try to give their children an advantage, of course, is a totally separate question.