I think WeChat's specific success in China was really driven by WeChat payments and QR code - both of which failed in the US. These two features were critical to support so many use cases that WeChat enables today (payments, peer to peer transfers, offline to online service). Yes the Chinese New Year helped garner interest and a lot of people use WeChat to send red packets, they also connected their bank accounts and started using it for payments. This is again in line with how WeChat launches every feature. They try to launch it in groups rather than getting each individual user to try it separately.