It would not surprise me if Castle Story is not generating enough weekly revenue as it is an established game. New games give higher revenue which is why S8 continuously releases new games. CS does not have the PvP driver that Dragon Story has as an example with no arena. So now they've been given the mandate to drive up revenue any which way they can including this tedious timed event no matter how much of their existing player base it irritates. And giving away essences is not going to force people to spend more gems. They do not want willing purchases of gems but rather want people to spend based on anxiety and fear of not completing a timed event.
Castle Story 2 is likely on the horizon, like Farm Story 2, etc.