Political Upheaval during the Early years of Islam.
From the very beginning, one of the most important factors that led to the political instability of the Islamic empire was the inexperience of the Arab people in organized government on a large scale. In pre-Islamic times the Arabian peninsula was a desert backwater, largely ignored by the rulers of the Sasanian empire. Life revolved completely around the tribe. Loyalty, hospitality and honor were the most important concepts in this world, and there was no other moral or ethical code. The concept of the individual was nonexistent. The tribes were governed by semi - democratically elected elders who settled disputes and made decisions. These tribes vied for power by raiding rival caravans and making war upon each other. Because there was no higher authority to settle these tribal disputes, the Arabian peninsula was a chaotic place. .
Therefore it is no surprise that these patterns continued during Muhammad's conquest of the Arabian peninsula and after the Islamic Empire was established. Muhammad used standard tribal tactics to build his empire, he built alliances, slaughtered the opposition, and any tribes that dared to oppose him. He used war to build a power base, just like any other tribal leader in those days. .
After Muhammad died in 632, factional fighting over his successor broke out almost immediately. The Khazraj clan of Medina attempted to elect their own chief. A coalition of Muslims who saw this as a threat to Muslim unity cut them off by electing a successor to Muhammad. Abu-Bakr, Muhammad's father-in-law and close advisor, won out and became the first caliph. It was agreed that though he was a successor to Muhammad he was not himself a prophet. Abu-Bakr was the first of the Rashidun, or rightly guided caliphs. These caliphs were companions of Muhammad who attained leadership by virtue of their close relationships with the prophet.