What the author says is correct but not complete - his reference to "Crusades" seems to end with the Fourth Crusade, wherein the Franks and Venetians plundered their Greek buddies in Constantinople. There were more, including the infamous Children's Crusade (which populated the Muslim slave markets nicely) and a number of "Crusades" that never left Europe and weren't pointed at the Holy Land or even the Muslims anyhow. A Crusade in this sense is simply the Church offering holy dispensation to its members in exchange for military activities on the Church's behalf - they "take up the Cross," hence "Crusade."
Furthermore, while the Muslims "won" the Crusades, the Arabs did not. It was during this period that political control of the Islamic peoples was wrested from the Arabs by first the Seljuk Turks, then the Ottomans. This control didn't leave Turkish hands until the secularization of Turkey and the fall of the Ottoman empire in 1917, at which time the Arabs marched into the Holy Land behind a fellow named Lawrence. Part of the Arabic grudge against the Christians and the Crusades is that the latter helped the Turks in this regard. It's a grudge half a millennium old, but it doesn't seem to have faded much. To us they're all Muslims, but they don't see it quite that monolithically.
There used to be caliphs (religious leaders) and sultans (political/military leaders); the former remained Arabic much longer than the latter, which term was actually invented to disguise Turkish suzerainty. Now the sultans are gone, and the return of total control to the religious wing in the form of mullahs and ayatollahs (a fairly new term) hearkens back to the earlier, bloodier era of Islam.
I believe that the Turkish control of Muslim world happened even without Crusaders from the West. It must have accelerated it, though. The first Crusade is the only one which achieved its goal. That is partly because the first Crusader fought Arabs rather than Turks. Arabs' main battle units are mounted soldiers with lances. This formation was easier to defeat than Turkish steppe formation made up of mounted archers. And their tactics emphasizing deception and speed all helped defeat subsequent Crusades. European Crusaders were fighting Turks not Arabs after first Crusade. Saladin was a Sunni Kurd. But his troops were all Turks. Eventually, Crusaders have become minor disturbance in Muslim world. Hashashin sect was more pressing concern for rules in Mid-East. Even Saladin had to compromise with Hashashins. A few different groups of Turks carved up entire Mid-East. Most of them first started as slave soldiers for Caliph. The slave soldiers were under direct control of Caliph of Baghdad, who can attack any political enemies of Caliph. Other ordinary Muslims balked at all-out war against other Muslims because Koran says that Muslims should not attack other Muslims. So if rival Caliphate appears, Caliph in Baghdad is in quandary. That is why they recruited Turks as if they were slaves, bought in the market. But in time, these soldiers took power from Caliph rendering him as a more figurehead.
Mongol invasion was repelled not by Arabs but Marmeluks of Egypt, Turkish soldiers who took over Egypt. Mongols were distracted by succession intrigue back home. So the troops in Mid-East at the time was not at peak strength. But anyway, they fought against Marmeluks. So this was battle between two steppe tribes from North and Central Asia, not Arabs. Crusaders ironically had great hopes for Mongols(!). They heard news that large steppe army were coming from Central Asia into Mid-East. Crusaders began to weave their wishful thinking into this news. Soon, Mongol army were seen as long lost Christian steppe tribe coming to help fellow Christians in need. When Mongols were going from Damascus, which they just conquered, to Jerusalem, Crusaders rode with them. This was a symbolic guesture of solidarity at the time. But soon Crusaders had second thoughts about true nature of Mongols. So they sent messenger to Baybar, the ruler of Egypt. They buried their hatchet and cooperated. Crusaders helped Marmeluks for safe passage through their area and set up for battle. Marmeluks won the battle near Jerusalem. So everybody was spared from Mongol carnage.
Mid-East was busy with bigger players than Crusaders in later years. Hashashins, Seljuks, Ottomans, Mongols, Marmeluks. Crusaders were minor players. They only held on to small strips of Land in Levant. Hardly a big loss considering that they have domain streching from Morroco to Central Asia.