The knight’s armor was useless.
– The reality is it was great and when Muslim forces captured large amounts of European armor, they used it.

The crusaders were just in it to steal wealth or land.

– In truth, most crusaders lost money, and fully expected to lose money, on their campaigns. Some crusaders were in it for number one, the medieval equivalent of corrupt defense contractors or something. But they were the exception. To fully understand this, you have to get a sense of how truly ad hoc the First Crusade was. They kept running into unexpected situations and had to improvise solutions on the spot. No one actually intended to go found the crusader states. But that’s how it worked out due to shifts in politics that played out in realtime.

The crusades opened up trade and learning to Europe, which was a cesspool of ignorance and economic stagnation prior to the crusades.
– The crusades expanded trade and expanded the flow of ideas, but they did not invent them overnight the way simple books will present it.

That crusaders didn’t bathe, weren’t cultured, etc.
– That one’s so wrong I don’t know where to begin. There’s this prevalent idea that crusaders were crazy barbarians who couldn’t even count, and the Muslim were like desert themed neo-classical humanists who would have invented Jeffersonian democracy if the crusaders hadn’t shown up. Here’s the reality. If you got a totally dispassionate third party to get in a time machine and go observe the middle east or Europe in the 11th or 12th century, nobody, on either side, would appear very civilized by today’s standard. But, they wouldn’t appear barbaric in comparison to each other, either.

That the crusades were caused by religious intolerance.
– Again, that one’s so wrong it’s hard to know where to begin. The geopolitics were much more complicated than that. Instead I’ll just throw out a little known fact that usually blows the minds of people who think the crusades were purely motivated by past people’s irritation at the existence of other religions. Here goes. If it suited their purpose, European crusaders would ally with Muslims. The middle east was basically city-states at the time due to the nature of the climate and ecology. So if a Sunni warlord got too big and dangerous, his Shiite and Christian neighbors would team up against him. If a Shia faction got too powerful, the reverse would occur. If and when the Christian crusader states got too big and powerful, the Shia and Sunni would set aside their differences to keep the Christians in check. Christians and Muslims also made treaties with, and against, their common alien culture, the Mongols. Those kinds of alliances could not have happened if the whole thing was about religious hatred.

The knights wore suits of solid plate armor.
– They wore chainmail. Plate harness wouldn’t be invented until hundreds of years after the end of the crusades. Roughly the same amount of time as separates flintlock muskets from automatic rifles, also separates full mail and full plate armor.

That Christianity was all one thing at the time.

– The reality was more nuanced. Just like Islam was already divided into Sunni and Shiite, Christians were already divided into Catholic and Orthodox churches. This made for endless political interactions and changes throughout the history of the crusades. On a related note, Catholicism in those days wasn’t nearly as focused on religious uniformity as people think. This isn’t to say that it didn’t have uniform practices at all. But it took the rise of Protestantism in the Renaissance to trigger an institutional obsession with ideological purity. Like plate armor, this was hundreds of years in the future. Martin Luther lived about as far from the crusading era as we do from King George II.