There were other popular social media platforms in the past, such as Sina Weibo and other online discussion boards, which were not heavily monitored as WeChat is.
Remember niubo, which ran from 2006 to 2013? https://baike.baidu.com/item/%E7%89%9B%E5%8D%9A%E7%BD%91 It is just a website, there is no technical difficulty to shut it down.
So none of this is really new. As technology and platforms have developed, the Chinese state has improved and expanded it's surveillance and suppression apparatus. I'm no fan of Xi and the situation has definitely worsened under him, but this is how the system works.