What if a group of people wanted to steal Bitcoin? Here's one way it could happen:
Fork Bitcoin (call it BTC2 for simplicity) so people have both sets of coins. Allow users to sell their forked coins for extra money to buy more BTC
Bitcoin forks seem like a great way to cash out and profit! Everyone sell your BTC2 and you can make some extra money. It's completely safe!
Fork Bitcoin AGAIN (now we'll call it BTC3), but this time without replay protection. Now, if a user sells you their BTC3, you could trigger a replay attack on BTC nodes (since the private keys are the same, and signed messages are as well). Now you get their BTC3, but you also get their BTC since the same signature can sign those coins over to you
