I agree that it's an interesting subject, especially the big differences in popularity of models and makes, often for no obvious reason.
Naturally, if a country produces vehicles, these will be popular in that area. In northern countries, the climate may play a role as well, so if a brand gets a reputation of being particularily prone to rust, it could/would affect the sales in nordic countries.
But in cases such as the Hiace, there are no obvious reasons for suddenly losing popularity.
Antenn, you say that the Hiace lost popularity in Hungary after the 1990s. Do you happen to know, which models buyers started getting instead of the Hiace?
Because I enter all my spots into a database, I can see, that in Denmark, french vans started taking over, once the Hiace was retired and replaced by the Proace in 2012/13. Once faithful Toyota buyers switched to Renault Master, Renault Trafic, Peugeot Boxer and Citroën Jumper (and also Opel Vivaro), but this was - as I said - much later.
The Hyundai H-1 never had big sales here, but I've noticed, that they tend to last long, so customers must be relatively satisfied.
Besta, I've never seen and the only E-Series I've recorded (and uploaded) was exported, which is probably no coincidence.