How are satire and sarcasm the same?

They're similar but they aren't the same. satire is a comedic way of making fun of something. Sarcasm is a way of stating wrong information in a way that is obviously not true.

sarcasm: the use of irony to mock or convey contempt

Satire: the use of humor, irony, exaggeration, or ridicule to expose and criticize people's stupidity or vices, particularly in the context of contemporary politics and other topical issues.

So from this i would say they are alike, and very close to being the same thing.