That may well be so, Japanese cars had an absolutely terrible reputation for being rustbuckets in the 70's so they had to do something about it. Given the number of them that were manufactured the fact that they are so rare today is as far as I know uniquely due to the rust problem.

Mazdas are still rustbuckets today.

Mazda mostly sorted out their rust issues by the 2010s depending on model. A couple decades late, but they're pretty good now.

Isn't the Mazda 3 a really, really popular and pretty well-regarded car?

Yeah, it's a good car. Until it rusts. Supposedly they've fixed the rust problems in the new Skyactiv models, but I'd be weary of any Mazda before 2018.

Oh so you mean it quite literally - that's it's very rust prone.

Interesting! Any information on what they did wrong?

I'd say the Japanese figured out how to make this happen on a cheap car. Almost all high end european cars (including Volvos) had great rustproofing for a long time but cost far more than Japanese cars. The Japanese made the first reliable and long lasting low priced cars.

I think that was what I wanted to say. Thank you for putting it more clearly.

(In my mind, European craft production results in pricey cars, whereas large volumes only make sense for cheaper stuff.)