From your own source please read carefully.
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"The current knowledge of Muhammad’s life is mainly based on sources such as
Ibn Hisham,
al-Ṭabarī,
Ibn Saʿd, etc. that are silent over Muhammad’s stop at Ghadir Khumm. Even when the writers mentioned the event, they said nothing about his speech. Similarly, western biographers of Muhammad make no mention of what happened at Ghadir Khumm. However the account of this event has been recorded by
al-Yakubi who is famous for his sympathy for Shiite cause, and it appears in canonical collections as in the
Musnad of Ibn Hanbal. Some Sunnis scholars do not deny Muhammad’s declaration about Ali at Ghadir Khumm, but they argue that he was simply urging the audience to hold his cousin and son-in-law in high esteem and affection.
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Even we accept that the prophet (PBUH) urged the audience to hold his cousin and son-in-law in high esteem and affection people didn't respect his request as we witnessed how he was treated after prophet departure.
Moreover at least there is en event by the name of Ghadir Khom regarding Imam Ali (as) Imamet while there is nothing about the other
caliphs .
Before Ghadir Khom , Prophet told people another Hadith that is known as narration of 2 heavy things:
I am leaving among you something which is very important and should be followed, you will not go astray if you get hold of it after I am gone, one part of it being more important than the other: Allah's Book, which is a rope stretched from Heaven to Earth, and my close relatives, who belong to my household. These two will not separate from one another till they come down to the reservoir, so consider how you act regarding them after my departure."
Clearly prophet of Islam says if you don't want to go astray you should follow these 2 : holly book and household and at the end it says these 2 come down to the pond which is pond of Kowsar which holly book clearly refers to it as prophet doughter Fatima Alzahra (sa) ... again no sign of other caliphs.
Why household? 'cause God in Holly book clearly has purified them from any sin.
Who is household?
3:61
Then whoever argues with you about it after [this] knowledge has come to you - say, "Come, let us call our sons and your sons, our women and your women, ourselves and yourselves, then supplicate earnestly [together] and invoke the curse of Allah upon the liars [among us]."
And whom prophet (pbuh) took by himself? Ali, Fatima, Hasan and Husayn .. base on these verse Imam Ali is equal by prophet "ourselves and yourselves" ....
Then we have this narration:
"He who dies without knowing the Imam of his time, dies the death of (the days of) ignorance (Jahiliyya)." – Prophet Muhammad (SAWA)
So there should a person whom if you don't recognized him you die the death of (the days of) ignorance (Jahiliyya) which means you didn't recognize Islam 'cause the only different between days of ignorance and now is Islam ... so it's very important , this Imam must be like the prophet not an ordinary person. who is he?
The most important Q about this narration is who was Imam of Fatima Al zahra (as)? surly none of those caliphates 'cause she died while she wan angry at them .. so either you say the 3 guys were caliphs which means she died the death of ignorance or there were not caliphs ...
the other narration is this :
"The (Islamic) religion will continue until the Hour (Day of Resurrection), having Twelve Caliphs for you; all of them will be from Quraysh."
Who are these caliphs?12 caliphs?
The other narration:
The Prophet said to Ali,
"Will you not be pleased that you will be to me like Aaron to Moses?” (Volume 5, Book 59, Number 700: Sahih Bukhari)
"O Allah! My brother Moosa implored You saying: 'O my Lord! Expand my heart and make my Amr easy and undo the knot in my tongue so that they may understand my talk and appoint from among my Ahl Haaroon, my brother, as my Wazir and strengthen my back with him and make him partner in my Amr.' You inspired him: 'We shall soon strengthen your arm with your brother and make you both dominant.' O Allah! I am Your Servant and Your Messenger Muhammad. I implore You to expand my heart and make my Amr easy and appoint from among my Ahl Ali, my brother, as my Wazir."
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