Why did the movement towards civilization begin later in Northern Europe than in Western Europe?

Western Europe was a little connected with the centers of civilization of the Ancient World back in the era of the Greek and Phoenician colonization of the western Mediterranean. It was they who founded the first colonies in the south of France. Then Western Europe was conquered by the Romans (1st century BC and 1st century AD), from them there remained as a heritage: Christianity, Latin, cities and the level of culture (aqueducts, baths, roads).

There was nothing like this in Northern Europe, even the Romans did not try to conquer something there.