After a series of random missions disconnected from the main narrative, Rick and Morty finally solved its Rick Prime problem. Rick C-137 got help from Evil Morty to kill the villain, which many assumed would make C-137 happy. However, Rick is in an existential crisis, compounded by the fact he has no purpose after avenging the deaths of his wife Diane and daughter Beth. This results in Morty trying to boost him up and resume their cosmic adventures.
Source:https://www.cbr.com/rick-and-morty-observers-marvel-watchers/