My question is regarding the events that led to khilafat. Whenever we mention Ghadeer e Khum, our Sunni brothers say that Moula means a friend and Abu bakar was chosen by Prophet (pbuh) himself. Like not directly but he (PBUH) asked Abu Bakr to lead the prayers as Imam, and Imam Ali prayed behind him!
And even if Imam Ali didnt prayed behind him yet he stayed silent over it? So that means he accepted it? Which makes Abu bakar rightful khalifah?

Please see this link which will answer your question: