Complex sentence: In the 19th century, traders and missionaries (chiefly Presbyterian) arrived, but the Tannese stuck to their traditions more strongly than other islands; there remain fewer Christians in comparison with the other islands of Vanuatu.
Split into simpler sentences: In the 19th century, traders and missionaries (chiefly Presbyterian) arrived. The Tannese stuck to their traditions more strongly than other islands; there remain fewer Christians in comparison with the other islands of Vanuatu.