Shanks Warned the Five Elder Stars About Blackbeard... Not Luffy
Why is Shanks a rat for telling the Five Elder Stars about Blackbeard? He already previously did a weird thing by warning Whitebeard about him. I mean, it's obvious he was trying to tell them that Blackbeard is plotting more than just World Conquest or something like that because he didn't want them to accidentally aid Blackbeard the same way Whitebeard did.
Ace being killed was the "trigger" for future events like Blackbeard killing Whitebeard and taking his Quake Fruit. Whitebeard underestimated him. The same thing is happening to the Five Elder Stars, right now. He's trying to avoid another catastrophe that allows Blackbeard to capitalize on another opportunity like that. He's being smart about it - probably the only person who is.
