There are two themes running through this most enjoyable querky movie; first, the random romantic encounter element and the sinister mysterious interventions preventing it from maturing; alongside this excitement there is - arguably - a deeply religious theme, whereby individual human destiny is embedded in a comple hidden Divine plan.
The key point being that each individual has free will to make decisions, but when these decisions lead away from the Divine plan for that person, 'circumstances' beyond that individual's control are subtly 'adjusted' so that he or she in response to changed circumstances effectively steer themselves back onto a path within the 'plan'.
Very clever, and a great denouement.