Going to crusades helps in getting the knightly order guild for that faction quite early as it gives +25 points(you need 100).
But taking the faction leader doesn't gives any extra points the game considers it as a general and nothing else. Though it makes the papacy more happy if a Leader or a heir joins and goes to the crusades.
btw the a old cheap trick to get a guild pronto is just before u storm the crusade target make all the generals in your home country to join crusade and after that conquer the city in the same turn. U get a guild, chivalry and morale bonuses and it makes the pope go super happy.
For any guild type you get +25 points for joining a crusade and +10 points for recruit knights from it. Apart from that only the hopitallers are Teutons get a bonus of +10 points if they share a border with a region that has islam or pagan religion respectively(have to be more than 50% and is one of the reason i don't capture stettin early in my HRE campaign).
We also get a +10 points if a catholic nation declares war on a islamic factions(Hospitaller guild only).
A chivalrous general having chivalry 5+ also gives a bonus of +5 points every turn in it's settlement.
That all u need to know about getting a Knightly order guild.
