I'm sorry, but Singapore came pretty close to collapsing in the 1960s, especially just after its expulsion from Malaysia. Just about only thing it had going for it was its geography. The UMNO in Malaysia was banking on Singapore asking to rejoin the federation on significantly more unfavourable terms than the latter got in 1963, after teetering on the verge of complete state failure.
Make no mistake—Singapore's prosperity today is no accident.
Your claim is essentially that cities, and therefore city-states, will naturally fall into wealth and prosperity. I wonder what happened to Athens, Venice, Genoa, and all the other merchant city-states, the equivalents of Singapore on the ancient, mediaeval, and early-modern world.
And they have fallen into relative obscurity, barring Venice. They're all not big, financial hubs pulling in hundreds of billions to trillions, like New York, or London, or Singapore.
The point is that cities don't accumulate wealth 'just because'. Wealth comes and goes. And this goes all the more for city-states with no hinterland nor strategic depth.
Compare Venice with Monaco in that respect. Or Hong Kong, which is waning because of that lost sovereignity but is still very rich. Or Luxembourg. Or Qatar. It's just great to be a small self-contained free port.
And Venice is not the worst place to be.
Now, we actually do not know what will be of Singapore in 50 years. May be many things.
Make no mistake—Singapore's prosperity today is no accident.
Your claim is essentially that cities, and therefore city-states, will naturally fall into wealth and prosperity. I wonder what happened to Athens, Venice, Genoa, and all the other merchant city-states, the equivalents of Singapore on the ancient, mediaeval, and early-modern world.