...am I misreading this chart?
DLC releases 6th of december, and there's a massive uptick in people playing. (Or at least opening the game to install the DLC and try it.)
Over the next week it drops off as expected post release as people now have the expansion installed and the novelty wears off - and they go back to normal play.
Then over the rest of the month to date it trails off to *where it was pre DLC*. That's not a massive or rapid decline.
Conversely, if you look at the release of Distant Stars, you can just about see it on the play chart, and there was no peak for release, just a continual reduction in players.
In fact for most expansions there doesn't seem to be a peak at release date - but rather a hump *before* release that then decreases through release and beyond.
the bump is on the 3rd, before the release, and it has a sudden drop, not a slow tapering, if you look at the january numbers you will see how it is well rounded, while the december numbers drop off suddenly then tapers, that is a much more sudden drop off than the other dlc's.