I’d say it’s the fact that even as time has gone on and reddit has gotten more casual users there is still a much higher percentage of “hardcore” users on Reddit versus other social media. Or at the very least the hardcore users have a lot more influence then on other social medias, since they’re the ones more likely to be posting content lots of people see and moderating content. As well as those users being a lot more likely to be willing to learn a new more complicated platform and more likely to be directly affected by 3rd part apps shutting down. This all combined means that the hardcore users the platform relies on are more likely to leave to places like here which without them will make the website worse and cause more casual users to leave.