For information of all, there were no historians present when Prophet Mohammad (S) was alive.
What we read today were written by Persian writers 150 to 250 years later of Prophet (S) death. Those writers were not an eyewitnessed to any event. They claim their books are based on hearsay and many learned Muslims think, in reality, they have invented fake stories and fake Hadees from their own minds and deviated Muslims away from Quran. They have very successfully replaced Islam deen of the Quran with their own fake Islam religion. A majority of Muslims ignorantly are the fake Islam religion. Only fools would accept their books.
Quran commands. Do not divide into Sects. Period.
All those divided into several sects like Sunni, Shia, Deobandi, Barailvee, Ahle Hadees etc are disobeying Quran as such they are all considered as non-Muslims. Do not trust them. They are the most dangerous people in the world.