I think Thirteen's promotion as the world's scariest coaster (when it was intended to be marketed as a spooky family ride, like Hex) was seen as a mistake, which got a very poor public response even though lots of people turned up initially.
Thirteen's marketing got the park's marketing director let go at the end of the year, The Smiler's marketing got the marketing director promoted to global head of Resort theme parks.
As for the dark theme, if its done well then who knows, it might still have the right humour & appeal (like Smiler) and not just pure bleak sinister. We've only just started the promotion.