Singapore is a safe banking haven in a sea of legal risk and chaos.
Singapore was effectively an (almost) empty plot of land when it was established, and it was designed to be an 'banking/commercial haven'.
What makes Singpore 'rich' is the foundation established by the UK as having 'rule of law' and 'peace and order'.
As long as Singpore remains peaceful and orderly, where the commercial law is respected and foreign entities trust that their money is safe and they will get a fair deal, and that ability is not available in surrounding nations (which it isn't, even today), they they will do well.
If you're a Western company looking for a 'gateway to Asia', then Singapore is a good choice. It was literally built to be that.
It's a little bit how Swiss standard of living is supplemented by the fact that 1/3 of the world's offshore money is parked there, and that surplus benefits the locals.
Like a more complicated version of having 'Oil Wealth'.
It is what it is, and we have to be careful about criticism from afar, but that doesn't mean we can't be critical.