The DLC bookmarks have nothing to do with it. When Sword of Islam came out, one of the most common complaints was that an Emir in Al Andalus would eventually start an invasion for Aquitaine and he would always win.
The Muslims get bored because they're too stable. They're too stable because Muslim traits causes every Muslim who has them to be loved by every other Muslim.
-Mujahid gives you +10 opinion with all Muslims and +30 with everyone who also has the trait (this stacks, so it's +40 with everyone who shares the trait)
-Hajjaj gives you +10 with all Muslims
-Hafiz gives you +5 with all Muslims
-Sayyid gives you +10 with all Muslims
-Mirza gives you +5 with all Muslims
-Ashari gives you +25 with everyone who also has the trait
-Mutazilite gives you +25 with everyone who also has the trait
THIS is why Muslim realms never fall apart. It gets even more ridiculous when the Caliph is being controlled by a human who can manipulate jihads so that every vassal and all of their kids get the Mujahis trait, creating a unified empire of love for at least a generation.
-Mujahid is the same as Crusader. No advantage
-Hajjaj is the same as Pilgrim. No advantage
-Sayyid and mirza is only available to specific dynasties and characters, with mirza being useful for a single character and not being inherited
-Ashari and mutazilite do give +25 with the same trait, but you forgot the -25 with the opposite trait, so the net opinion benefit is null. No advantage
Muslims have, at best, a +15 opinion advantage over christians, and that is not even considering the huge opinion maluses related half brothers and demesne maluses related to high decadence (which are almost ubiquitous when we are dealing with large realms, which are coincidentally those blessed by the sayyid trait).
The point is, muslim stability has NOTHING to do whatsoever with their traits (which, as i just demonstrated, provide no significant advantage over the christians), but everything to do with their inheritance laws. Turkish open is probably the best inheritance law in the game and is decisive in keeping muslim realms from fracturing. Add the absence of Elective demanding factions, and we have the real reason for muslim dominance in this game