Mulroney did warn against underestimating Trudeau,  but he didn't support him.   Under the populist political environment,  only then populists would win am the election.  Bredxit, Trump, Wynne, Trudeau were all populists.  No consistent good policies were given during the election. 

After Wynne's majority win, I correctly predicted Trudeau's win, and warned in this forum not to criticize Trump in case he would win the US presidency.  I noticed that Democracy is under seizure,  right after Wynne's win.