One can say the same about the Crusades also.
I'm not ignoring the religious aspect of the crusades, but when one looks at the leading figures and the majority of the crusaders, it can be easily noticed that the crusades were most attractive for the barons who were looking for more land, for the peasants who were running away from the usurers, from debts and from poverty and it was especially attractive for the younger siblings, who due to the right of primogeniture (the right of the firstborn son), where the oldest son was inheriting everything, were forced to look for land and wealth somewhere else.
After all, look at the greatest success of the crusaders : invading Byzantine, the Christian Byzantine.
What i want to say is that no war was purely religious, but religion was used as a tool to attract the masses.
Then again, the history of the Ottoman Empire says something else. Those Christians who accepted islam were given all the rights the leading class enjoyed, while those who didn't convert to Islam were always oppressed, killed, forced to pay much higher taxes and many more taxes. And it was happening for 5 centuries, until the first decade of the 20th century.
Also, since they were spreading Islam (not in a peaceful way) can't we say that these wars were also religious? (i'm asking this since you said the Crusades were the last purely religious wars)