Abolfazl Sabouri, Abolfazl Sabouri is based in New Zealand and has an MA in Jurisprudence and Islamic Studies. He is a graduate of Elmiyeh seminary in Qom with more than 15 years of study and research where he has... Answer updated 6 months ago

It is because of different ahadith.

The position of the hand in prayer may not be very important, but a scholar must determine who he should refer to after the demise of Prophet to receive the his Sunnah, and  he should know that who is his Ulolamr. Should he refer to the Ahl al-Bayt or he can refer to the companions of the Prophet, even though some of them, they don't know deeply about Islam?

The followers of Ahlulbeit are called Shia and the followers of companions are called Sonni.