From the papacy of Adrian VI in 1522 to the election of John Paul II in 1978, every Pope was Italian. Was it a conscious decision for the Popes to be exclusively Italian? Are there any historical or political reasons this was the case?
Basically the reason is that the College of Cardinals used to be majority Italian throughout most of its history. That changed under Pius XII in an effort to modernize the church and bring it into the modern, international era. The Italians lost their majority in 1946 and at this point the cardinals are just over 20% Italian. That drastic change has made it much easier to elect non-Italians pope.
Before 1522, there was still more direct political pressure on the papacy, most notably the French forcing the election of seven successive French popes during the residency of the papacy in Avignon in the 14th century.