1. He was an invader. William's claim to the English throne was based on the fact that he was the nephew of the late King Edward the Confessor. However, there were other, stronger contenders to the throne, including the English-born Edgar the Ætheling. By invading England and defeating Harold Godwinson at the Battle of Hastings, William effectively imposed his rule on the country against the will of the majority of the people.
2. He was a ruthless conqueror. In order to secure his control over England, William carried out a brutal campaign of subjugation. He ordered the mass slaughter of thousands of Saxons and Normans, including women and children. He also burned down entire villages and towns.
3. He imposed a foreign system of government on England. William introduced the Norman feudal system into England, which replaced the existing Anglo-Saxon system of government. The feudal system was based on the principle of lordship and vassalage, and it gave the Norman barons a great deal of power over the English people.
4. He suppressed the English language and culture. William tried to suppress the English language and culture in favor of the Norman language and culture. He encouraged the use of French in the government, the law courts, and the schools. He also promoted the building of Norman churches and castles.
5. He created a society based on racial inequality. William's invasion and conquest of England created a society in which the Normans were the dominant group and the English were the subordinate group. The Normans had far more political power and economic opportunities than the English.
As a result of all of these factors, William the Conqueror was not a legitimate king in the eyes of many of the English people. He was seen as an invader, a conqueror, and a usurper. He never fully gained the trust or loyalty of the English people, and his rule was marked by resentment and unrest.