Why were the Shia Muslims angry with the Sunni Muslims after the death of Muhammed?

After the death of Prophet Muhammed, Muslims had a disagreement. Sunnis believed that Muhammed's successor should be Abu Bakr and Omar, and the Shias believed that his successor should be Ali.

Explanation: The main conflict between them -

   Though the two main sects within Islam, Sunni and Shia, agree on most of the fundamental beliefs and practices of Islam, a bitter split between the two goes back some 14 centuries. The divide originated with a dispute over who should succeed the Prophet Muhammad as leader of the Islamic faith he introduced

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explanation: