Why did William of Normandy claim the thrown?

William of Normandy claimed the English throne based on his assertion that he had been promised the crown by King Edward the Confessor, who was childless and had supposedly named William as his successor. Additionally, William argued that Harold Godwinson, who was crowned after Edward's death, had sworn an oath of fealty to him, which he believed legitimized his claim. This combination of alleged promises and oaths provided William with a basis to invade England in 1066, leading to The Battle of Hastings.