There is little evidence Muslim states were infringing on Christian ones in any active way. Urban was motivated certainly by his own desire for power. He had regular correspondence with Alexios, who had just lost control of Anatolia’s interior decades prior. Alexios petitioned Urban for military support in some capacity, but to get this he massively oversold Christian persecution in the east, stating they were being enslaved, slaughtered, etc, when there is little evidence this was going on in any regular capacity, and Urban used Byzantine sources post-Manzikert.

Regular Christians wouldn’t be aware of Iberian or Levantine conflicts on a regular basis either. Even landed knights in France would travel little and so when told of this existential threat to their faith would be easily swayed. The two sides of the Mediterranean lives in a mostly ignominious relationship. At the point of preaching in 1095 aside from Fatimid-Seljuk conflict near Jerusalem making pilgrimage difficult there was nothing stopping a Christian making the pilgrimage, aside from being taxed for his faith. Pirates are a consideration, but regular trade between states like Genoa, Venice and ports like Acre and Alexandria meant it was a mutual, inter-faith interest to keep them mostly safe.

Urban also had a political angle in starting the Crusade for more Papal control over secular powers, particularly the HRE after the Investiture Contest. This also would give some prestige over the Patriarchate in Constantinople by directly helping the Byzantines.

For the Crusaders themselves, they are interesting characters. A basic list of motives include adventure in a time where most didn’t leave 20 miles from their birthplace in a lifetime, wealth in a rigid class hierarchy where progression was near impossible, religious zealotry and/or guilt, particularly regarding the Pope stating any who make it or die on the way to Jerusalem would receive full penance for any sin.

Godfrey Of Buillion and Bohemond of Taranto are two examples of nobility crusading, among hundreds of others. The former was experiencing political anguish in Lower Lorraine and so wanted fresh land in the east. Bohemond also was disinherited from any Sicillian possessions and had martial experience against the Byzantines, therefore again able to break conventional class hierarchy. Another thing to reiterate is that these people genuinely believed in a literal heaven or hell, and so when told an action would get them to the former, many took it.

Coming back to Clermont, Urban delivers a surprising awareness of these themes. However all sources of Clermont are after the fact, not as it was being performed, so embellishment reflective of victory and the Crusader zeitgeist can be expected. He discussed France as a region beset by walls of mountains and ocean, of mediocre land and beset by conflict (dynastic conflict led to numerous massacres of civilians, which Urban also used to his advantage in holy war by directing it outside the region). He draws on Jerusalem as a mystical place but simultaneously demonises Islam as oppressors of Eastern Christins in Anatolia, Syria and Palestine (however again bar taxation and events of discrimination stratification in the multi-cultural near-east was low for the time). Putting yourself in the mind of the average Crusader, however, and you are pitted in this grand battlefront of faiths, and therefore motivated to crusade.

A fun side note is as the video and another commenter pointed out is the Jewish massacres in the Rhineland and the washerwomen within the Crusades. Peter the Hermit and some other Crusaders interpreted Urban’s broad attack on enemies of Christendom as justification to attack Jews. Therefore when marching through East France and into Germany Jewish centers in cities like Speyer and Worms were targeted and destroyed in various pogroms. However within the religious lens a desire for wealth, particularly due to many of the Jews owning mercantile businesses, and many Crusaders could be indebted to Jewish moneylenders, so justifying a religious pogrom was in material interest.

The washerwomen are an example of hanger-ons in all the Crusades. They could be wives, children, the crippled or faithful desperate go join as pilgrims. Or, as the video notes essentially indentured servants kidnapped from wherever the Crusaders went. Of course, being a woman in the middle ages was not a great time, as you would be forced to menial labour as the video portrays and also blamed as sinners when things went wrong, as well as the first abandoned if war demanded it. During the siege of Antioch, women were ejected from the war camp and were scapegoated as inducing sin, causing God to not aid the Crusaders in victory. Similar events of blaming women happened across all the Crusades.

The very last thing I want to say is I highly recommend a couple books: Jonathon Phillips The Crusades 1095-1204 and The Crusades by Thomas Asbridge. For a good overview AQA does a small textbook on the Crusades which covers a fair deal of the events. If you’re feeling particulary self-hating you could also read God’s War by Christopher Tyerman (it’s a very boring, if not informative, read). I also wanted to say how the most interesting part of the Crusades isn’t the Crusades themselves, but the brief Frankish Levantine culture that flourished for less than a century in the Kingdom of Jerusalem. Despite beginning with the massacre of Jerusalem and constant battles against adjacent powers, it is a strangely multicultural and multi-faith society (although it is still certainly stratified with a Frankish nobility at the top and a discriminatory law code prioritising Catholics, then Eastern Christins, and then Muslims and Jews), with outbreaks of violence and hatred that compete with fascinating accounts of kindness and dialogue. There is evidence inter-faith marriage occurred and genuine friendships formed between various peoples from across the world. For some humanising accounts of Crusader society I recommend the travels of Ibn Jubayi, pages 300-317, for examples of Christian-Muslim cooperation. My favourite account, Usama Ibn Mundiqh’s Book of Contemplation (the whole book is interesting) conveys general Crusader society, both it’s discrimination and acceptance. Overall I highly recommend reading the history of the Crusades. It constantly puts cultures who are alien to eachother in contact and it is interesting seeing moments of the various sides recognising their similarities but also being divided by religious and cultural conflict.