The motives could be many. It might be obsession. Maybe the stalker has developed an unhealthy fixation on the recipient, perhaps because of something they saw or heard about them. It could also be revenge. If the stalker feels wronged by the person in some way, they might use the mail to intimidate. Another possibility is mental illness. Some people with certain mental disorders might engage in stalking behavior without fully understanding the inappropriateness of their actions.
I'm not sure specifically as there could be many different 'Madison game stories'. It might be about a character named Madison in a game. Maybe it's an adventure story where Madison has to overcome various challenges in a virtual world.
Yes, the Ashley Madison affair is a true story. It involved a significant data breach and exposed the personal information of many users of the website.