The short version: that's when Xi Jinping took power and started very quickly undoing all kinds of moves toward moderation and reform that had been undertaken by the previous few leaders.
He ramped up control over the population, consolidated power for himself and cracked down on dissidents/party criticism.
The 2014 bit is more subjective, but going from memory that's when I started to regularly see semi-mainstream technology, business and politics publications focusing on problems/concerns with China.
Seems like many of those who provide services to the government are familiar with the Berry Amendment and the implications of the “qualifying countries” list.
Things have been on a strong downtrend since 2012 and alarms have been ringing loud since around 2014.
Edit: Anyone writing a business plan including sensitive technology sales to the US government should DEFINITELY have seen this coming in 2016.
Edit2: Also, candidate Trump had loudly been yelling about China for over a year at that point