Bernie catching up to Hillary is exactly the same as Trump's dominance of the GOP field. The anger is genuine and justified, and the people who are angry are morons. Therefore they cannot focus their anger on the real target, Washington corruption. They are blinded by their hatred of those who think differently than they do. That, of course, is exactly what the corrupt politicians want. Fight each other instead of them.
What they are betting on is that people are too stupid and blinded by hatred to unify against the real enemy. So far, they are correct. The American people are so stupid they are willing to see the country be destroyed, rather than find common ground with fellow American citizens that they hate.
Neither Trump nor Bernie can save us. Only we the people can save America, by being non-partisan and unified. In other words, we're doomed.