That's a technological advance and not a policy change. WeChat didn't exist prior to 2011 and Xi Jinping rose to power in 2012.
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.