OCP did not resolve the problem, per se. OCP bought them more time to allow the (delayed) effects of the increased standard of living to manifest themselves fully. They didn't really _need_ OCP - they would have ended up in the same place either way, OCP just made it a bit shorter, and reduced the strain on economy (and hence decrease in the standard of living) on the way there.
https://www.theguardian.com/world/2015/oct/29/china-abandons...