Brent, please listen the truth. If you don't believe me, please please please Google the things I am about to tell you.
They changed it because they realized what the disastrous unintended consequences were, primarily the "4:2:1 Problem". (Please Google it so you can see that I am telling you the truth)
4 grandparents
2 parents
1 child
Children provide for parents and grandparents in China. With no brothers and sisters, one person now has to support six or more parents and grandparents and it is becoming an enormous burden on the current generation. And that is exacerbated by the fact that the life expectancy has increased dramatically. Even without the One-Child policy, birthrates are still falling and China may soon start to experience a drop in population. This will be disastrous for their economy because there won't be enough productive members of the population to support the increasingly older generation.
Then there is the "Missing Women of China" (please Google it so you'll know I am telling the truth)
With the one child policy, females were aborted and often killed after birth because, among other things, male children could better care for their parents (going back to the 4:2:1 problem). So now there is a huge disparity in the male:female ratio, which in turn has caused a whole host of new problems.
And the "Little Emperor Syndrome". (please Google it so you'll know I am not making this up)
With four grand parents and two parents doting on one child, especially a male child, many in the the younger generations are spoiled brats.