Complex sentence: With the baptism of Poland in 966, the old pagan religions soon disappeared over the next few centuries; however Christian Poles coexisted with a significant Jewish segment of the population.
Split into simpler sentences: With the baptism of Poland in 966, the old pagan religions were gradually eradicated over the next few centuries during the Christianization of Poland. Nevertheless, Christian Poles coexisted with a significant Jewish segment of the population.