Why was not a republic established in England, but a monarchy?

England became a monarchy back in 1066, when William I “seized power” and called himself king. It so happened that Great Britain retained this form of government, despite the fact that most political scientists (experts) consider the monarchy to be a relic of the past.

Parliamentary monarchy is a form of government in Great Britain. The country has a parliament, a prime minister. The British cannot change the monarchy to the republic, because this is a historical tradition.