My impression is, as someone said earlier, that the Crusades varied a great deal. It’s hard to generalize about them.
However, some things are worthy of note.
The Arabs did, indeed, conquer the Middle East by the sword. Early on, when Christians were still the majority, their rule was fairly benign. Still, Christians were discriminated against in a number of ways. As their numbers decreased, Arab rule grew harsher.
Still, it was relatively benign until the Seljuk Turks conquered the Arab rulers. It was the Seljuks who denied access of Christian pilgrims to Jerusalem. That was the precipitating cause.
It should be remembered that the Arabs did not appreciate the Seljuks either, for the most part. When the Crusaders came, and after initial bad contact, Arabs actually lived in peace and relative harmony with Crusader rulers. Ordinary people, Muslim, Christian or Jew, did not much care who their rulers were, because Arab rule prior to the Seljuks had become just as feudal as Europe. It didn’t matter too much who lived in the castle. The residents of the castle normally didn’t treat the peasants too harshly, because their own livelihood depended on them.
Not infrequently, Arab Muslims and Christian crusaders joined together in feudal battles against common enemies.
The real end for the Crusades came when the Mamluks turned down offers of Crusader alliance in fighting the Mongols and drove the Crusdaders from Palestine. The Mamluks defeated the Mongols, but not before the Mongols had ravaged a good part of the Middle East; a ravaging from which it never reallly recovered. A later Central Asian (largely Turkic) force under Timur swept in and destroyed what the Mongols and Mamluks didn’t. In the meanwhile, yet another Turkic group, the Ottomans, had taken over formerly Byzantine Asia Minor. Timur and the Ottomans fought each other to a mutually wrecked standstill. Timur’s death ended the domination of his forces, the Ottomans then divided the Middle East between themselves and the Persians. Ottoman misrule is legendary.
Some believe that the Ottomans “saved Europe” by fighting Timur to a standstill. However, that is made doubtful by the increasingly difficult time the Mongols had earlier when they moved into the periphery of Western Europe; an effort which the Mongols ultimately gave up. Neither their army nor that of Timur was well adapted to the narrower battlefields and damp climate of Europe, where heavily armed, extremely well-trained knights and wooden bows (rather than compound Asian bows) held the advantage.
In the context of the truly awful history of the Middle East, say what one will, Crusader abuses were minor and their rule was actually pretty benign, on the whole. They had actually reached a point in which they lived in mutually beneficial, peaceful co-existence with the next-nearest power; the Arab rulers of Egypt. The latter, however, were deposed by the Turkic Mamluks, and the rest, of course, is history.