I’d argue that the IOC has an even more pressing worry in mind: Not ZERO candidates, but ONE candidate… and that candidate is either a thoroughly unrealistic one clearly not suited to hosting such a large event, or an utterly unpalatable one representing a controversial regime. Dismissing those cities by choosing something “better” (LA, Paris, London, Tokyo, etc) is one thing; looking elsewhere when they are literally the only candidate is a great deal more embarrassing for all involved.