At the time it was enacted, the one-child’s policy’s goal was to conserve resources. It was also intended to prevent pollution and the spread of disease.

It was a direct response to overpopulation concerns (Club of Rome, Limits of Growth, etc).

Not only did it horribly failed, it did the exact opposite.

By encouraging industrialization, it resulted in more resource consumption, more pollution, and more disease.

It created an immense amount of wealth, and increased standards of living. But those weren’t the goals.

It was intended to avoid an apocalypse, not create a utopia.

If a time traveler went back in time and told Chinese leaders the effects of the their policy, they might very well outlaw contraception.

Edit: earlier family planning policies were focused on maternal health.