Did they 'move' to Wechat? I went to school and made friends with chinese students. They were already on WeChat, and made a Facebook account after coming to the U.S. I agree, though, that they seem to have left Facebook.
How does wechat monetize, or does Tencent just eat the cost?
I don't know how wechat monetizes but Line has been fairly successful with sticker sales and pushing apps.
Line makes TONS of money from their apps. I'm not sure how much their stickers make. I read a story about the average user spending $12 for line run/jump (not sure what the name was, but some infinite runner or jumping game).
wechat monetization is mobile gaming. A single game can generate $20M+ per month and wechat have many of them.
I see everyone using FB in southeast Asia.
As for China, I don't think most people can access FB? Don't you need a VPN?