Trudeau's resignation came after Canada's Deputy Prime Minister Chrystia Freeland stepped down in mid-December. On her way out the door, Freeland cited her differences with Trudeau on how to approach Trump's presidency and his proposal for tariffs.
In contrast to the mincing, cautious, nicey-nice approach of most leaders these days, Trump's method in business and politics is often to apply pressure to a target and see what happens. With Canada, Trump is determined to pursue long-standing trade and tariff complaints to a resolution on his terms. Knocking Trudeau out of power makes that more likely and moves Canadian politics in a more congenial direction toward a new Conservative government.
More broadly, by hammering Trudeau and Canada, Trump makes clear to allies and adversaries alike that he and the US are not to be trifled with.
ya’ll can hammer, hammer, hammer then
Maybe get a wallop this time