Problems with

Question

I don't see why the correct answer would be in the imperfect, since the coming of the tradition is something that has happened and is over with. The imperfect doesn't work. The correct answer should use the passe compose: Cette tradition, qui est venue....>>

Accepted Answer

Hi Max,
"This tradition, which came originally from European settlers, has gradually permeated ..."
This text is giving historic background information and the "tradition" is not a completed event, it is enduring.
This is why I don't agree that it should be in passé composé.
This is how I see it.
Jim

Answer

This is background information - imparfait regularly used. Additionally, Imperfect does not mean incomplete/uncompleted - in appropriate circumstances, it refers more to vagueness of time and duration, This external link may help further. https://www.frenchtoday.com/blog/french-verb-conjugation/passe-compose-versus-imparfait/