I’m going to take this as evidence that OP travels through time in the opposite direction. From their perspective, the microwave was dirty, so they put a bunch of popcorn and a paper bag in it. All the mess jumped into the bag, and the microwave became clean.
Chronology is hard, I get it. But you’re supposed to microwave a soap-soaked sponge for cleaning, then microwave popcorn for eating.
I’m going to take this as evidence that OP travels through time in the opposite direction. From their perspective, the microwave was dirty, so they put a bunch of popcorn and a paper bag in it. All the mess jumped into the bag, and the microwave became clean.