Kingdom of Jerusalem , first Crusade

I have always wondered what would have happened if certain events would have went any other way ... so here it is one of the main theme is the first Crusade the part of history that fascinates me the most. How did a small amount of people managed to create something out of nothing ? What would have happened if they would have failed ? What would have happened if the first crusade would have had the same effect as the one lead by Peter the Hermit ? What if the war would have broken up between the Crusading army and the Bysantium empire? (Which did again in the other crusade) All this and more i  will try to tackle ...
 So please join in the discussion if you have anything to add....