"This is just the beginning of the college implosion," Mark Cuban tweeted last week, after the news about Sweet Briar, an all-women's college in Virginia.

Cuban, the well-known entrepreneur and billionaire investor, was not surprised by the news. For years, Cuban has warned of a "student loan bubble" created by skyrocketing tuition fueled by an endless supply of student loans. 

"At some point, it's going to pop," Cuban told Business Insider in a recent interview.

Here's how to fix the bubble, according to Cuban. Congress needs to pass a law that caps the amount students can take out from private student lenders. That would be more useful than focusing on students' current debt, he said.