The amount of content continuing to come out for the game, with no additional monetization, is pretty amazing for these days, and much appreciated. No gaas. No subscriptions. No battle pass. Just improving the game for the playerbase (substantially) with no fuss or muss.
I guess it's a combination of passion for the project and having enough money to live comfortably. ConcernedApe is a treasure and I hope the industry keeps shifting towards indie devs and companies that have this philosophy of making games for the fans and not for the money.