Facebook Fans: What triggers to “like”?

Why we follow specific Facebook fans page of company?
What triggers to follow/like and ufollow/dislike, is there spesific triggers?
Follow the development of the company, for example: with the case “Volkswagen emissions scandal” If people unfollow or follow the Facebook fans page or social media that company has? We have to look backward of the event that already happen.
You can also use the tools to analyze like Quintly(tools).
Could you identify 10 to 20 example cases that increase or decrease the number of followers of social media that company has.