I see the two part finale as the show making fun of itself.
Like, they start off with the idea that they fixed the show and made it less crazy, meaning they accomplished everything they wanted to do with the 'Save Greendale Committee', and we see Abed trying to find a fun story in what's become a normal school.
Then, they find out the school is going to be sold off. Jeff and Britta start to accept it and move on, accepting normalcy, and right at that moment Abed and Annie come in yelling "TREASURE!!!!" And it turns into probably the most absurd story we've seen in the show. It sort of comments on the way the show can be equally comfortable being realistic and being ridiculous.