Canada overplayed its hand
Saudi Arabia is very important global player. First of all, it is a pillar of petrodollar system, therefore providing much of the strength of US dollar as a global reserve currency. To put it briefly, if you want oil you need US dollars, and Saudi Arabia guarantees that. Second, it is undisputed leader of Gulf monarchies and de facto leader of Sunni Muslim world (although Turkey tries to take over this position but this is another story). Saudi Arabia controls Islamic holy sites , and with their money and strong ties with US their word has weight. Finally, it is part of US-Israeli-Saudi axis which acts as a significant force in Middle East. Considering all of this, Saudi Arabia is practically never criticized by Western governments (and rarely by media) for human rights abuses. This stands in stark contrast to countries like Iran (where for example women actually have vastly more rights then in Saudi Arabia, and of course system is much more democratic) .
Canada, on the other hand, on international scene is viewed simply as an appendix to US. There is preciously little Canada could internationally without US support. Although current leftist Canadian government tries to distance itself from current US administration, as we could see from this example, they are basically toothless when left to their own devices.
US silence on this matter has clearly left Canada isolated and vulnerable against full political power of Saudi Arabia. So, they are trying to make amends without loosing much face, clearly accepting their second or third rate status in international affairs. It is now only a question how much humiliation would satisfy Saudi Arabia to restore status quo ante.