The vast majority of the federal debt was generated by Trudeau 1.0 who increased the federal debt by almost 1000% (in a time of double digit interest rates to service it).  

This handcuffed Mulroney with interest payments amounting to 35-40% of the operating budget just to pay annual servicing charges on Trudeau's debt.  Without savage budget cuts - and the Liberals and their Rat Pack opposed even timid spending cuts - the debt continued to increase.  Mulroney's part in the debt was minor.  He balanced the operating portion of the budget 5 of  9 years with minor operating deficits the other 4 years.

Finally, through Mulroney's free trade and other initiatives to grow the economic pie and his GST initiative to increase the federal slice of said pie and through lower interest rates PLUS the Chretien government's savage cuts not to Fat City but to the provinces and the poor the budget was balanced.

But even today we are paying off the Trudeau 1.0 debt.

And the Trudeau 2.0 debt awaits.