Really? I guess your definition of "quite different" is different from the usual. Would you care to expand?
Language and culture across Scandinavia is very similar, and Finland's culture is different only to a small degree if at all
Instead, I would point out various socio-economic factors, such as Sweden having a higher rate of ethnic minorities (generally over-represented in COVID-19), Norway's GDP being far higher than the others (thanks to fossil fuel) and Sweden having a far greater population in elderly care institutions, compared to Finland.
A great deal of the deaths in Sweden come from nursing homes, where you had the situation that caregivers would travel from one institution to the next, spreading the virus.