It’s not a pretty picture, as described in this article in Salon:
Donald has followed in his father’s corrupt footsteps. Trump’s career is littered with bogus businesses (like Trump University); repeated ripoffs of suppliers, contractors and employees whom he failed to pay for services rendered; and the misuse of the Trump Foundation to feather his own nest while trying to look like a philanthropist. Six of Trump’s businesses have gone bankrupt. Despite this, on April 18, 2015, Trump tweeted this falsehood: ”For all of the haters and losers out there sorry, I never went Bankrupt.”
Trump has also lied about the size of his wealth, as various business publications have pointed out. Many observers suggest that one reason Trump has refused to release his tax returns is that they will show that he has repeatedly and wildly exaggerated his wealth and thus his success.
Given this background — his lackluster academic record, his dependence on his family’s connections and wealth to get into college and to succeed in business, and his troublesome and abusive business practices — it shouldn’t be surprising that Trump is so insecure about his intellect and so thin-skinned about his accomplishments.