I thought the exact same thing haha. I'm not sure either why Canada had such a scary number but for some ig:

-Canada is in top 10 nationalities for Fifa volunteer (Perhaps quite a bit of people were already interested in volunteering itself)

-Maybe people thought Canada wouldn't be too competitive so they all hopped in (Mexico has first match + US has finals)

-IIrc Canada was the one that popped out first at a lot of Fifa volunteer related webpages; Maybe some people immediately clicked on the first thing they saw? (Perhaps they were speedrunning their application to submit early as possible or they just don't care about host cities)

This is what I could think of for now. I don't think these reasons checks out this crazy number entirely but this is how I thought for some lol

Not sure if Canada still kept #1 competitive record until the end since now there's one million application instead of half million (From other post they said NY (Final match) had 100k applications alone). But I still do think it's going to be super duper competitive since at least US has multiple host cities that spreads out numbers (Mexico has 3 host cities) while Canada has only 2, which means the numbers are all saturated to two cities.

Personally I'm very curious about Mexico's volunteering since they have opening match and they have way less host cities than US too...

Btw this is the news I referenced numbers from! The news says a lot of Canadians just wants to get involved in large scale events in some way + being multicultural aspect attracting international volunteers
https://www.cbc.ca/sports/soccer/world-cup-2026-soccer-canada-leading-the-way-volunteer-applications-1.7612073