Angry Asian Man notes how adoptions from China have fallen and he asks: "what drove the trend of all these children adopted from China. Was it simply the fact that it was so easy, with so many children up for adoption?"
I would say this played a huge role in it - China had a large, available supply of babies with relatively easier procedures compared to other countries. It may seem cold to frame transnational adoption in market terms but supply and demand play a fairly substantial role in explaining trends, especially within an international context. I know there are some folks out there with far deeper knowledge on transnational adoption to chime in!