Why did Trump impose 50% tariffs on Canadian imports?

Trump imposed the 50% tariffs after talks with Canada broke down and a Friday deadline passed without a trade deal, in what was reported as a significant deepening of trade tensions between Washington and Ottawa [1]. Canada, under Prime Minister Mark Carney, responded by suspending negotiations and pledging dollar-for-dollar retaliation, ending days of cautious optimism that a deal had been close [2]. A separate report notes Trump later postponed the threatened 50% tariff just hours before it was due, saying a deal in principle had been reached pending finalised documents [3].