That last part is a paraphrase, but the first part is a direct quote. It's something Donald Trump actually said. Via Politico:

Donald Trump broke from his usual political script for part of a campaign rally on Wednesday to offer advice for success to his college audience. One boastful tip from Trump: “Always be around unsuccessful people because everybody will respect you.”

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And you’ll find that when you become very successful, the people that you will like best are the people that are less successful than you, because when you go to a table you can tell them all of these wonderful stories, and they’ll sit back and listen,” he said. “Does that make sense to you? OK? Always be around unsuccessful people because everybody will respect you. Do you understand that?”

Donald Trump has been flat out telling his supporters that they are marks during this whole campaign. He's been saying it out loud this whole time. He loves the poorly educated. He loves those who are less successful because they'll believe the bovine fecal material he perpetually slings in every direction, since he has been successful. And he knows he can get away with it because he's skilled at picking marks.

This of course explains the cadre of losers and incompetents he has used to staff his campaign - who have screwed up at every opportunity and cost him a ton of delegates in the process. Trump isn't interested in competence, he's interested in being around people who give him the kind of glowing reaction he feels like he deserves. People who will listen to his stories with rapt attention and nod and tell him how brilliant he is.

Actually competent people don't behave that way. When they are put in charge of a task you've given to them, especially one that you don't understand yourself (e.g., maximizing your delegate allocation in a Republican primary), they will push back if you ask them to do something wrong. They will tell you that you don't know what you're talking about if you give them a bogus instruction.

Good leaders welcome this from their subordinates. Donald Trump has no interest in it, so he purposefully surrounds himself with unsuccessful sycophants whose only professional goal is kissing Donald Trump's posterior with the most grace and flair. And it looks like, at the end of the day, that this might end up costing him the Republican nomination.