When he instead gets flattened into an accordian shape, that's funny. Another example is the title graphic at the top of this page. When you tell a joke and no one laughs, that's funny because you didn't expect that to happen. So if you tell a joke and no one laughs, it is polite to laugh hysterically. Everyone else thought your joke was great, so they returned the favor by doing something funny for you too.
Political jokes are popular because they're lies about liars.
If a United States president is portrayed as a giant vending machine handing cash to a donkey, that's funny, because it's a lie. Probably what really happened was he gave the money to an elephant and a guy with a scythe. This type of humor is both untrue and unexpected, so it's doubly funny. For instance, if a big fat cartoon character like Elmer Fudd tiptoes behind a skinny little tree and hides, that's funny. If a skinny little cartoon character like Bugs Bunny hides behind Elmer Fudd, that's not funny.