I'm just a beginner who is about to take a course related to the fourth crusade next semester. Recently I've been reading Geoffrey of Villehardouin's The Conquest of Constantinople; in the book Geoffrey mentioned that when the pilgrims besieged the city, king Alexius just ran away although his army outnumbered that of the crusader's. I'm wondering why did he do that? ( the author interpreted this incident as "the miracle of Our Lord".) And what is the actual situation? Did the crusaders just took over the city easily?

Also, as I'm not a Christian and know only a little bit about this field, are there any additional books I can read to acquire more knowledge?

Thank you guys, this is my first reddit post and there might be some format and grammar problems. Sorry about these in advance!