Queen Elizabeth II of England did not become the leader of Great Britain through being elected or through a rotating leadership system. Instead, she became the Queen through hereditary succession.
1. Her father, King George VI, passed away in 1952, leading to Elizabeth's ascension to the throne.
2. As the daughter of the previous monarch, she became Queen Elizabeth II, following the tradition of monarchy in the United Kingdom where the crown passes from one monarch to their direct heir.
3. The British monarchy operates on a hereditary system where the title and responsibilities are passed down within the royal family.
In summary, Queen Elizabeth II became the leader of Great Britain through the hereditary system of monarchy, where the title passes from one monarch to their direct heir, rather than being elected or appointed.