what happened between 1965 and 1970?
"The Great Escape From the Countryside". Calculate small farm + born 1948-1955 (the "big generation") and theres 5-6 kids in their 20's and one small-hold farm. Small-hold farming became unviable back then. Also the same time you can see Helsinki population skyrocket. See all those concrete ghettoes with their 1960-1970's architecture? Guess who inhabited them? Finnish society changed from predominantly agrarian to predominantly city-dweller. Many villages virtually emptied. (And thats why theres so many "country hicks" in Helsinki

)
Emigration? Helsinki couldn't cope with the movement. And as for jobs, Swedish economy was booming and passport/work permit restrictions had been lifted in 1956 or so already. "Everyone went to Sweden", to work in Trollhättan or Göteborg... Thats why you get a "return from holiday" bonus. So you'd come back from Sweden...
As you can see the emigration/immigration goes in about 10 year cycles. The 1965-1970 exodus and then a 1975-1980 immigration rise. Its not like it would be "foreigners", though theres quite a lot of Swedish citizens. The guys who had gotten their Volvo and house money and/or didn't want their kids to be called "Finnjävel" moved back into the "old" country, as the Finnish economy was on a wobbly way up. But they wouldn't move "back to the village". The old farm house if it even exists is "granny's cottage", but the people settled into the cities.
But as you can imagine, this is why anyone frothing about moving to Nowheremäki gets the "silly looks". If the local young people have been and are still are moving out because theres no jobs for them, and they have the language/education/nepotism all figured out, how would you expect some funny foreign guy being suddenly desirably employable? Yes, that is why living in Nowheremäki is cheap - because nobody wants to move there. But as for jobs... ask how many villagers got a cousin in Sweden.