The argument is that developing the mineral resources in North Korea, will cover the costs of developing the Country.
The possibility exists that once the mines, railroads and ports get built, and Western business get entrenched, that the North Korean Government will become rich and powerful like China’s did, and Western politicians will no longer be able to pull it back, under pressure from their corporate donors - like they did with China.
Political liberalization does not follow automatically - likely not at all.
Singapore is a dictatorship that’s clean, safe and very wealthy .
But it has no freedoms. Great place to live if you can accept that trade-off.
I think Trump held the meeting in Singapore to show that an authoritarian government can exist that has a free market and respect for human rights.
It didn’t have to be an either/or situatin, but both.
If North Korea does become a Singapore, it’s still progress where it is important.