You didn't build that
I know a lot of smart, hard working people who aren't rich. I know rich people who are lazy as the days is long. Rich people aren't rich because they're smart and hard-working. They're rich because they found a way to get rich. Many times it's because of connections, who they know, or access that they have. I know rich people who aren't very bright at all. I know poor people who are smart and work really hard, but don't find money to be the most important thing in their lives, or chose a vocation that isn't well compensated by our free markets, like nursing.
I'm no Billionaire, but I've had some success in my life. I've put in a lot of weekends and late nights and 15 hour days and gone to bed for months at a time with chest-pains to get it. At the risk of sounding like douche, I've got an IQ that I'd put up against about anybody's. And yet, I'm not rich. How does that work?
And, even for the success I've had, I have to credit much of that success to people who cared about me: great family and public schools with teachers who invested of themselves in my success and access to higher education, and great people who inspired me. Yes, it's true - I've worked REALLY hard for whatever success I've had. But THAT's only one factor in the equation.
"Somebody helped to create this unbelievable american system that we have that allowed you to thrive.
Somebody invested in roads and bridges. If you've got a business, you didn't build that. Somebody else made that happen."
I wish our normally eloquent and articulate POTUSA had said "you didn't build those roads and bridges on which your business relies". In context, it's quite clear THAT THAT's what he meant by THAT "THAT".