why do the Finnish people speak a language that is not indoeuropean while they are indoeuropean ?

Answer 1

The Finns are an incursion and are not Indoeuropean. Their language originates from the Uralic group from Siberia.

By the way, Hungarians also do not speak a Indoeuropean language.

Answer 2

With regard to the ancestry of the Finnish people, the modern view emphasises the overall continuity in Finland's archeological finds and (earlier more obvious) linguistic surroundings. Archeological data suggests the spreading of at least cultural influences from many sources ranging from the south-east to the south-west following the geographical realities with gradual developments rather than clear cut migrations. The closest genetic relatives of Finns are found in Estonia and apart from that, in Flanders and Germany.

The possible mediators and the timelines for the development of the Uralic majority language of the Finns, are equally uncertain. Through comparative linguistics, it has been postulated that the separation of the Baltic-Finnic and the Sami languages took place during the 2nd millennium BC, the proto-Uralic roots of the entire language group dating perhaps from ca. 6-8th millennium BC. As the Finnish language itself reached a written form only in the 16th century, not much primary data remains of early Finnish life and so the origins of such cultural icons as e.g. the sauna (a bath), the kantele (a musical instrument) and the Kalevala (national epic) have remained rather obscure.

Answer 3

they speak the older Nordic language, that had been handed down through many generations.