Everyone's busy and their inbox is already full. Why add to the problem with a longwinded email? People generally like short, concise emails better than long ones because concise emails have an obvious focus. Plus, when your users are scanning through all their emails in a short amount of time, they're more likely to find the overall message before deciding to take any action.
The goal was to drive an emotional response from the email campaign. More than 12 million unique emails were sent, with the email content personalised to the individual recipient with information on distances the subscriber had travelled, interesting facts such as how many football pitches that would be and other destinations they could have travelled too.