It's simple, really. Because they can.

Recall when China's Foreign Minister, Wang Yi, visited Canada in June and verbally attacked a Canadian journalist for daring to ask about human rights abuse in Canada. All the while, PM Trudeau sat in silence, like a dunce, allowing this barrage to continue.

How insulting to our nation and how embarrassing! What a display of arrogance and hubris by Foreign Minister Yi.  So back to your question: he did it because he could. Nowhere else on the planet would this be allowed. Nor should it be.