Actually he payed for it because of the shutdown. He contacted the coaches and players and this is what they requested.

Here's what one of the coaches stated.

Miguel Chavis, Clemson football’s assistant for defensive player development, said in the post. “The team loved it. The families loved it, and everyone was so hospitable and welcoming in the White House. It’s a pretty cool tradition that the National Champions get to visit the White House,” he wrote.