"Why is it that the Canadian government made such an enormous award to Khadr…"?

Because the Canadian government was complicit in the torture and illegal incarceration of a Canadian citizen. The Harper government was warned by the Supreme Court that it was failing in its duty and the government ignored that warning and instead doubled down and used Khadr as a whipping boy for its favoured "it's-us-against-them" wedge issues. 10 million is probably cheap.