This comparison between Mulroney and Trudeau is silly. Trudeau created the deficit. He handed a terrible fiscal mess to Mulroney that was created during his tenure. To say that Mulroney was worse than Trudeau is tantamount to saying that the guy who did not put the fire out is worse than the guy who started the fire.
A better comparison is would Mulroney have run up a deficit from scratch the way Trudeau did? The answer is probably not, since Mulroney did produce budgets that were balanced with the exception of interest payments - payments that wouldn't have existed if there had been no deficit in the first place.
Also, this criticism of Mulroney can surely only be made by people who actually weren't around or aware of the political environment in the 1980s. Every time the Tories tried to cut spending, the Left and the Liberals went absolutely bananas, even for minor cuts. The shrill Rat Pack, lead by that horrible Shiela Copps, would stand up in Parliament and scream that cutting the deficit was "doing so on the backs of the poor" and "betraying Canada and the Canadian way" by "becoming like America". Its particularly gauling coming from the Left since the Left demonized Mulroney and the Tories for trying to be like Margaret Thatcher and Ronald Reagan. People like Maude Barlow and Bob White, as late as the mid-90s, were arguing that cutting deficits were part of a "corporate agenda".
So, in short, Mulroney did not cut deficits because there was no political appetite to do so. Canadians didn't want deficits to be cut.