Why is Queen Elizabeth II successful?

Answer 1

Queen Elizabeth II is queen because the Act of Settlement (1701) provides that since the death of Queen Anne and William III, the senior descendant of the Electress Sophia of Hanover in agnatic primogeniture shall be the monarch of England unless he or she is a Catholic and unless he or she marries a Catholic. The Act of Union (1707) made this law apply to the United Kingdom. From 1936 (before the Queen's accession) until 28 May 1972 His Majesty's Declaration of Abdication Act modified this rule to exclude the Duke of Windsor from the throne, but that has been dormant since he died.

The Australian Constitution provides that whomever succeeds Queen Victoria as sovereign of the UK is Queen of Australia (known as king is male). Queen Elizabeth succeeded Queen Victoria by the operation of the Act of Settlement in conjunction with His Majesty's Declaration of Abdication Act and that made her Queen of Australia.

In short, Elizabeth II is Queen because Parliament made a series of laws to have that effect.