The split of Muslims into Sunnis (who recognize the Sunnah – a book of interpretations of the Koran) and Shiites (who do not recognize this book, and also do not recognize the legitimate caliphs – the Umayyads and Abbasids) occurred in the 660s, when Muawiya defeated Ali and other “military democrats ”Among the Muslims and founded the Umayyad dynasty. Later, many opponents of the Umayyads, for example the Persians, declared themselves Shiites.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.