> Surely a de facto dictatorship like this shouldn’t be so wealthy and successful[...]
It's also worth noting that the entirety of Singapore just barely exceeds the area enclosed by Washington DC's beltway.
Whatever their form of government, small city states are always going to be able to avoid many of the pitfalls of larger countries. There's effectively only one level of government to deal with, and the despot is always going to live down the road from you and need to use the same public services as you, so you don't get the sort of disconnect e.g. Rome or the British Empire had from its provinces or overseas holdings.
It's also worth noting that the entirety of Singapore just barely exceeds the area enclosed by Washington DC's beltway.
Whatever their form of government, small city states are always going to be able to avoid many of the pitfalls of larger countries. There's effectively only one level of government to deal with, and the despot is always going to live down the road from you and need to use the same public services as you, so you don't get the sort of disconnect e.g. Rome or the British Empire had from its provinces or overseas holdings.