Being from Normandy, was he directly descended of Vikings?
I'm not sure. They spoke French, and France is considered a Romance language, meaning it evolved from Roman Latin. And I forgot to mention, to William's credit, unlike his father, he was never known to have taken up any mistresses, which (unfortunately) tended to be common for European noblemen.
In 1051, Edward the Confessor, the Saxon king of England, sent word to William, his cousin, that he had made him his successor in case he had no sons of his own. But William was not without his rivals for the throne. His most bitter was Edward's brother-in-law, Harold Godwinson. He was just as tough as William, and was the oldest son of England's most powerful and feared family.
In Edward's later years, Harold and his family did all they could to flatter the king into giving Harold the throne. And it seemed to have worked, once Edward died in 1066, Harold was crowned King of England. And as you can imagine, when William heard the news, he wasn't very happy.
Determined to have his revenge and his throne, William gathered an army of Normans, and they sailed across the channel to England. It's said that once they reached the shore, William gathered two handfuls of sand, and shouted to his men, "See how I take the land of England with my bare hands!"
Harold was only months into his reign, and he had not only William threatening him, but also his own brother Tostig, and Harald III the viking ruler of Norway. But while Harold's forces quickly dispatched Tostig and Harald, he'd greatly underestimated William.
The events that led to William becoming the first Norman king of England, starting with Edward making him his heir, are depicted on a 230 ft long embroidery called the Bayeux Tapestry, which was commissioned by William after he became king. Plus, it's amazing that's survived for almost a thousand years, mostly intact.
https://upload.wikimedia.org/wikipedia/commons/f/fe/Tapisserie_de_Bayeux_31109.jpg
According to the tapestry, the two armies, almost equal in number, met at Senlac Hill in Sussex. The Saxons at first seemed to have the upper hand, given that they knew the land. At one point, someone cried out that William had fallen, but William quickly got back up. He threw back his helmet so his troops could see he was still alive, and he ordered them to finish off the Saxon army.
Through a series of feigned retreats, the Norman army lured the Saxons to isolated areas at the bottom of the Hill, where the Normans hemmed them in and unleashed on them. Two of Harold's brothers perished, followed by Harold himself, supposedly by being shot clean through the eye to the brain by an arrow. Upon hearing of the death of their king, the Saxons fled into the woods. But even then, the Normans followed them.
Harold's body was buried without ceremony on the beach where William had landed. In fact, when Harold's mother offered William gold to reclaim her son's body, she was refused.
But despite William's victory in the Battle of Hastings, he knew that he wouldn't hold on to England without capturing and taking control of England's most important towns and cities, especially London. And in fact, by the time he got to London, his reputation had become so feared that they surrendered merely after William and his army encircled the city.
After which, William met with the kingdom's leading nobles and archbishops, and they swore an oath of loyalty. Finally, on Christmas Day 1066, in Westminster Abbey, William was crowned the rightful, and first Norman king of England.
But even then, there were rebellions from the Saxons for the next five years. The most ruthless counterattack from the Norman army was at York, where hundreds if not thousands of Saxons were massacred.
But despite his fearsome reputation as a warrior king, William also had castles built throughout the English countryside, the ruins of which can still be seen. He also constructed the Tower of London. He brought concepts like common law and a centralized government to England for the first time. And of course, had the Normans not come with their French language, English as we know it now would probably have sounded very different.
After reigning for 21 years, William went on a campaign defending his Duchy in Normandy, which he still had despite becoming king of England, and from either illness or injuries sustained in battle, he died in 1087.
Surprisingly, on his deathbed, he expressed remorse for the way he'd treated the Saxons and made them second-class citizens: "I fell upon the English of the northern counties like a raving lion. I subjected them to the calamity of a cruel famine, and by doing so, became the barbarous murderer of many thousands, young and old."
In the end, he was entombed in the Abbey of Saint-Étienne, located in Caen, Normandy. The original tomb was destroyed in 1562, during the French Wars of Religion, during which William's bones were scattered and lost. Only one thigh bone was left, and that's all that's left of him in a new tomb that was constructed for it in the same Abbey, and is the current one there today.
Forgot to mention, he left the duchy of Normandy to his oldest son, Robert. And since William's second son Richard had died 12 years before William, he passed the crown of England down to his third son, William II (Called "Rufus" for his red hair).