We humans are not as logical as we think we are.
Our decisions are driven heavily by emotions and feelings. In fact, a Harvard professor says that 95% of purchasing decisions are subconscious. We make decisions based on emotion and justify it with logic.
So if you want people to take action, you need to make them feel something.
From something as small as liking a post to something as big as joining a movement, people do things when they are emotionally triggered. The deeper the feelings are, the easier the decisions are made.