Who's to say they did? Who's to say they were broadcast to us from Mars? Who's to say we didn't all have a collective hallucination?

You have no evidence or proof than any videos were tampered with or fabricated. End of story. In formal logic, it is impossible to prove a negative ("Who's to say they didn't..."). You can only prove positive statements. You do that with evidence. Just because you can ask a question does not mean you have a disproof. It only means you don't know the answer.