Satan was killed in quite the graphic manner, but being a fallen angel, he really can't die. And in the world of South Park, he was redemmed. Matt and Trey will probably leaae it at that and not address who would take over Hell now, much like there are loose threads from S20 and S21 that may never get tied up.
It's said that Satan's grunts and groans came from Doom's Pinkies, the first demons you face in that game.
ManBearPig still has a whiff of climate change around him, but here he's treated as quite the real monster, killing off individuals instead of whole towns and nations as man-made climate change would do. Meanwhile...
The town still carries a bit of apathy seen since the first episode, where guns at school have become so normal that no one bats an eye at them anymore. Now that climate change is here and people can sense it, the talk has moved on to how to even get the ball rolling on didcussions about how best to worry. It's procrastination being spoken out loud.