There is some percentage of cars crashed in the first week. It only takes a few of these to cancel out the average of extreme outliers like your car.
For reference I have never seen an odometer with more than 200 000 on it before. Even most classic rebuilds I have seen like 69 Corvettes have some high 100K count on them, some event have reset odometers.
If I had not bought my car (it was at 300 000 km) I'm pretty sure it would have been sold in Eastern Europe instead, or maybe Africa since it's a Peugeot (a 406).
In the countryside, it's also very common to have both a nice recent car, and an old reliable one like mine for the dirty work. Most people I know do have one car that is a few 100 000s of km. Also, we mostly use diesel here, and these are supposed to be much more reliable than the gasoline engines used in the US (and I'm not going into the purported lack of reliability of American cars to begin with). I'm talking about everyday cars that are 15 or 20 years old, not classic cars.
Replacement parts on these are also far more expensive. New turbo is a four-figure number just for the part. Injection pumps are bloody expensive, too.
Less optimized designs may also be a factor. CAD and FEM modelling has only become better with time, so back in the day engineers would rather make a more conservative design, nowadays that's not so necessary any more.
Perhaps they don't build them like they used to, but our 1980's Honda sedan also easily clicked over 350,000kms too.
Turns out it has gone round the clock...