Between the 8th and 11th centuries the Christians in Western Europe were dealing with their own problems and invasions. Hispania (modern Spain and Portugal) was entirely conquered in the 8th century; Gaul (modern France) was invaded and partly conquered in the 8th century; the Alps were conquered in the 10th century.
Battles were being fought against Muslims at Covadonga (718/722), Toulouse (721), Tours (732), Narbonne (752-759), Lutos (794), Pancorbo (816), Syracuse (827–828 ), Clavijo (834), Ostia (849), Albelda (851), Guadalacete (852), Syracuse (877-878 ), Zamora (901), Fraxinetum (931), Acqui (935), Sardinia (1015-1016), Sicily (1061-1091), Barbastro (1064), Sagrajas (1086), and dozens more too. There were victories and losses, but the Muslims were being slowly pushed out of the West.
During this same time period, Western Europe was also dealing with devastating raids and invasions by the Vikings and Magyars. In addition to this, Western Europe was largely divided politically, with the exception of the Carolingian period (c. 774-888 ). After the division of the Carolingian Empire, Western Europe again fell into political chaos and division. There were also ongoing missionary activities in this period to convert the Slavs, the Magyars and the Norse, who were still mostly pagans and persistent threats to the West. These threats did not end until the conversion of Moravia and Poland in the 10th century, and the conversion of the Magyars and Scandinavians around 1000 AD.
So there were many good reasons why Western Christians were tied up in their own affairs and could not simply call a Crusade and go traveling to the Holy Land with large forces. It took several centuries to convert, unite and fight Islam and paganism in Western Europe before they were able to fight in the East.
The Fall of the Roman Empire and the barbarian invasions set the West back several centuries, so they hardly had a "massive technical advantage for several centuries".
The reason why the Arabs were able to spread so rapidly in those centuries is precisely because there was a power vacuum thanks to the barbarian invasions and the dissolution of the Roman state and military.
The Protestants also supported the Muslim Turks in their invasions of Europe and actively collaborated with them on numerous occasions.
Martin Luther urged his followers to look at the Turks in the best manner and even went so far as to say that some of his German contemporaries "actually want the Turk to come and rule, because they think that our German people are wild and uncivilized – indeed that they are half-devil and half-man" (The Ottoman Empire and Early Modern Europe, by Daniel Goffman [2002] p. 110).
Suleiman the Magnificent, the Sultan of the Ottoman Empire during Luther's time, sent a letter to Luther's followers in Flanders, Holland which stated that he felt akin to them since: “they did not worship idols, believed in one God and fought against the Pope and Emperor” (The Ottoman State and its Place in World History, Kemal H. Karpat, p. 53).
Suleiman extended his kinship further and wrote letters to German princes who were sympathetic to Luther to form an alliance with him to fight both the Emperor and the Pope as well giving protection to Luther and Calvin's followers in Hungary and Transylvania. In fact, one of the biggest collaborators with Suleiman was a Unitarian, John Sigismund, who not only was dependent on the Sultan for rule of Hungary, but the establishment of this heretical Unitarian Church of Transylvania.
In the Battle of Lepanto in 1571, among the Ottoman forces were to be found Lutheran and Calvinist allies from Holland and England. This treachery continues and in the Battle of Vienna in 1681, the leader of the Protestants in Hungary, Imre Thokoly in conjunction with the Ottoman forces was attacking Vienna. The Islamic scourge was prevented from succeeding with Vienna, as they had done with Constantinople, thanks to the Catholic forces.