The trigger factor that led to the end of the Personal Rule was the introduction of the Arminianist Prayer book into Scotland, which caused intense rioting and eventually led to the Bishop’s Wars. In England, reformation of the Church had been ongoing for many years. Charles had already imposed his Arminianism among the English church; changing the prayer book and introducing new measures such as kneeling and confession during worship. Religion was still a divisive issue; although there had been no serious opposition to this reformation, people still viewed the religion with suspicion. In Scotland, people saw Arminianism as being dangerously close to Catholicism; a religion which was feared and hated. The introduction of the Prayer Book into Scotland signalled a huge threat to the security of their faith, and when it was first implemented, people would respond to readings of it by rioting and violence. It was a step too far and seemed to threaten their liberties - Charles was forcing them to change their beliefs, beliefs which were suspiciously close to Catholicism. The riots eventually developed into Charles being at war with Scotland, leading to the end of the Personal Rule. It could be argued that the reactions of the Scots was unexpected, meaning that the end of the Personal Rule was also sudden and unexpected.
Before the Bishop Wars, Charles had been able to raise adequate revenue for himself through dubiously legal ways of collecting taxes; such as Ship Money, forced loans and knighthoods, or fining people for living within Royal grounds. The declaration of war, however, meant that Charles became financially unstable and he had no choice other than to recall Parliament to ask for money. This would effectively bring the Personal Rule to an end; and because of this and the sudden beginning of the Bishop Wars, it could explain why its ending was sudden.
However, on the other hand it could be argued that the ending was inevitable, and the Bishop Wars were merely a contingent factor which triggered the ending of the Personal Rule. For this view, there is seen to be underlying conditional factors which meant that the Personal Rule was always going to end at some point and could not have continued indefinitely. The king had many financial difficulties, and had always relied on Parliament to supply him with a sufficient revenue in order to start a war, or commission a new building. From this, it could be seen that the ending was inevitable, as the king would eventually run out of money and would need to recall Parliament in order to obtain money. Charles’ financial problems provide the conditions in which the ending of the Personal Rule could have happened, whilst the Bishop Wars provide the conditions in which the ending of the Personal Rule had to happen and why it happened at that time.
In conclusion the actual ending of the Personal Rule could be seen as sudden and unexpected as no one had anticipated Scotland’s strong reaction to the introduction of the Prayer book and the resulting Bishop Wars which led to its end. However the ending of the Personal Rule at all can be seen as inevitable, as it was to be expected that Charles would eventually need money to continue his rule and would have to recall Parliament. To summarise, the actual timing of its end was unexpected and sudden, but the fact that the Personal did end was not.