Oh he didn't have to quit. That was a political decision by Trudeau. Morneau as soon as the news broke of the financial dealings, he "paid back the $40k in travel expenses I had forgotten about".

Trudeau made a calculated political decision - Moreau could hurt the chances of the Liberals staying in office, so he had to go. It also avoided a separate inquiry into Morneau, but at least we'll see what the inquiry finds about the charity overall.

And beyond the Conservative party, nobody in Canada seems to really care.