Fred made a lot of money, especially compared to his son or his father, but he nonetheless inherited a business and sizeable amount of money from Friedrich Trump. I wouldn't call it Middle Class for the time period.
Yeah, it's Worthington's Law in action. I cannot reference this enough, because this is actually how many people think. I cannot believe how many conversations about Elon/Donnie/Bezos/Gates, etc all ended with the equivalent of "yeah, but he makes more money than YOU!" (which I nearly always sound not very distant from "My dad can beat up YOUR dad!". It's pathetic.