Yes people who speculate on real estate often buy and plan on selling in a few years. Whether they do a few renovations or think they've bought in an areas on the cusp of gentrification there are buyers who do speculate on what will be the hot market in the future. The majority of buyers buy knowing they should buy something that would be suitable for them for 5-10 years. Would add that the housing market does need to be cooled so I expect that there will be some measures put in. This crazy market is not actually good for Canada. Also not good for Australia who have essentially essentially similar housing markets. Too much of the economy is dependent on housing construction, the cost of housing has risen significantly faster than salaries, many have used their potential house value as a piggy bank or are counting on the sale of their home to fund their whole retirement, many will still have a mortgage in retirement when that used to be almost unheard of, the younger generation won't be able to afford a home and many baby boomers are too dependent on the potential equity in their home for retirement but haven't factored in the cost of a smaller home in that area is still very expensive, etc. could go on.
The person got lucky and bought when Montreal was still very affordable. Montreal is getting less affordable which will change Montreal dramatically. Same thing happened in the east part of Berlin and Berlin in general. Used to be pretty affordable, could be more artsy and have more character because the cost of living was pretty affordable. No longer affordable so the character of the city changed.