I get that it's a chicken & egg situation in Britain, but the appearance of the merch available in Poland is usually superior to this country, and doesn't normally start and end with a race shirt and a polo top. I bought some Janowski merch where I last visited Poland, just because it was a decent looking tee that had a cool speedway design on it - I don't think I could name a more boring and forgettable top-level rider than Janowski, but I still bought his merch because it looked decent.
It's a completely different animal, yes...but it's the exact same sport. Why is it virtually the national sport? Why is it tribal? Why is merchandising a big business? I don't think Poland has any big secret that they're keeping from us, it's still 4 riders/4 laps/etc/etc. They just do everything better.
They don't have PL football to compete with but they still have football clubs who average 10,000+ every match, basketball clubs that average 15,000+, volleyball is very popular, gridiron is popular, etc. It's not as if it's some sporting backwater where the choice is speedway or nothing.