History shows us that crusades conquests in ME were both religious and political.
Here are some bits and pieces from wikipedia regarding middle ages in Europe.
“The Catholic Church was the major unifying cultural influence, preserving its selection from Latin learning, maintaining the art of writing, and a centralized administration through its network of bishops.”
“Bishops were central to Middle Age society due to the literacy they possessed. As a result, they often played a significant role in governance.”
“New kingdoms like Hungary and Poland, after their sedentarization and conversion to Christianity, became Central-European powers. Hungary, especially, became the "Gate to Europe" from Asia, and bastion of Christianity against the invaders from the East for the next 600 years.[14] The Papacy, which had long since created an ideology of independence from the secular kings, first asserted its claims to temporal authority over the entire Christian world. The entity that historians call the Papal Monarchy reached its apogee in the early 13th century under the pontificate of Innocent III. Northern Crusades and the advance of Christian kingdoms and military orders into previously pagan regions in the Baltic and Finnic northeast brought the forced assimilation of numerous native peoples to the European entity.”
So under the light of these quotes we can say that crusades raid was religious in the sense that Muslim Seljhuk Turks were not only expanding towards Europe but they were taking islam and its influence with them , therefore Europeans under bishops/church influence probably felt that they had to protect themselves from cultural (religious) invasion.
It was political in the sense that the only way to stop Seljuk Turks and the dominions of Saladin which was all islam from further ethnic expansion was trough the raids of Crusades(Europeans) under the Christian slogans towards the holy lands to war for counter-influence, this is why I think crusades found the solution in capturing Jerusalem and that’s why they thought Jerusalem had to be liberated from Muslim control.
http://en.wikipedia.org/wiki/Middle_Ages#Crusades