There would always be some relative that would step up as the next magic hat wearer.
The Line of Succession is defined by The Act of Settlement of 1701 which said the throne would descend to “the most excellent Princess Sophia, and the heirs of her body, being Protestants”. By some calculations that’s about 5,000 people.
And that’s before the vested interests decide that some distant foreigner is eligible to sit on the throne for - reasons.