This kind of grinds on me a bit.
I'm not here to white knight for anyone, but I feel like people keep bringing up this point more than late night comedy shows share the same jokes.
It's just inaccurate, and I'll tell you why:
First, City Skylines has always been increasing in player count since it was released, and finally peaked off at the release of CS2.
Second, it stands to reason that people who play or have played CS don't exist in a vacuum cut off from CS2.
Cumulatively, there are now more people playing both games than there ever was before, with less people playing CS1 than CS2.
So a large portion of the existing playerbase preferred switching to CS2 and purchases not showing up in the "currently playing count" are like landmines, they could come up at any time.
So, any way you want to slice it, the community is bigger now than it ever has been.
Edit: If you want to accuse them of splitting the fanbase, then yeah, maybe you'd have a point there.