The number for Iceland is the only one that surprises me. The rest exemplify the general trend in the West in modern times: religion has been on the wane and irreligious people are not as interested in baby-making as religious believers.

Let's not get fooled by reputations. We may think of Spain, Portugal, and Italy as being very religious countries, but the Catholic Church more or less gave up trying to do its job starting with Vatican II. Turkey has had a secular (and secularizing) government since Ataturk. Hungary, Estonia, and other Eastern European nations were under Marxist indoctrination for more than forty years. In the Balkans (e.g., Greece), religion is more a marker for ethnicity than a guide for living life.

Much of the positive side of the ledger for population in Western nations is due to immigration of people who are induced to have children either as an act of piety (Muslims in Europe) or as a matter of custom (Mexicans in the United States). The above chart does not contradict this.