Why did England get involved in the crusades?

If you have played Medieval Total War:Crusades and listen to the story line its because the of religion. The pope wanted them to spread the Word of Christianity accross the world and convert or destroy anyone who oposed.

The Middle East including Jerusalem was as Christian as Europe when the Roman Empire fell, and continued so until Islam arose in Arabia and invaded and conquered it, forcing the surviving Christians to convert to Islam or die, or pay oppressive taxes, depending on the policy of the Caliph (Moslem tyrant) of the moment. Once Moslem rule was consolidated by such means, most rulers (no doubt eager for their money) allowed European pilgrims into Jerusalem. Near the end of the 11th century, the Moslems turned intolerant again and oppressed pilgrims (e.g. enslaving them). At the same time the Seljuk Turks arrived from Central Asia, converted to Islam, and began ripping apart the Christian Byzantine Empire, e.g. massacring the Province of Armenia after the battle of Manzikert (Turkish genocide goes back that far). Byzantium appealed to Rome for help and the Pope called a Crusade. The Crusaders took Jerusalem BACK in 1099, along with bits of the Levantine littoral, like Antioch (once a major Christian patriarchate and still probably majority Christian), but did not advance further (as they might have), having little ambition for rule beyond the Holy Lands. Many observers have remarked over the centuries, that if only the Crusaders had been more imperialistic, their kingdom could have lasted longer. The Crusades had NOTHING to do with "spreading Christianity across the world" -- they didn't even know how big the world was -- the great age of Christian missions was still centuries in the future (after 1492), -- or with "converting or destroying anyone who opposed". The irony is that this moronic slander sounds more like Islam than Christianity -- although even there it would still be an exaggeration.