He may appear to be naive but he probably did the calculations. It was a choice between pissing off Americans or Chinese.

For him, the most important relationship was with Americans, especially in the middle of re-negotiating NAFTA. Given the fact Trump can be so flippant, he could easily kill NAFTA and leave Canada so proverbially up the creek without a paddle. In his mind, he thought he might be able to appease Chinese somehow...but NOT this time around. If China did nothing, it was going to be open reason on Chinese executives and China had no choice but to nix it in the bud.