You're failing to take Paradox's lifecycles into account. Even though they're only the publisher, keep in mind that they're used to supporting games for 8-10 years after launch. Cities: Skylines came out in 2015 and has seen continual development ever since. Its performance was also abysmal at a point, but people kept playing and the devs kept improving it to the point where nobody even fully remembers why we cared about SimCity going to shit when Cities: Skylines was right there.