Bernie Sanders cannot beat Trump in the 2020 election. Although he does have many supporters, he doesn't have enough. The thing about it is that he may look as if he's going to win, like Hilary Clinton did. But, ultimately, he won't. Many of Trump's supporters, for whatever reason, don't let others know that they support him. It seems that Bernie Sander's supporters don't mind saying they support him. That is the reason that it may appear as if he is going to win but it's all false hope for his team.
Come election day, once again Trump will take the stage as the winner. There will be a lot of dissappointed Sanders supporters because many love him and not as many hate him as they do Trump. But all said and over with, Sanders just doesn't have what it takes to win.