I know what you mean, but that's not the way it panned out. They didn't choose him. Bernie himself made the choice and committed to the pledge of complying with the results. Because if he'd ran as an Independent, the messages he's been delivering for a long time, usually to an empty floor in the house, would've gone largely unnoticed. Not only did the majority of the public hear them and respond in positive affirmation, but both resulting candidates started using them. But with divergent intentions of course.