Существует немало версий этих причин.
Но на данный момент имею сказать следуюшее:
интересная инфа о Мозе (правда 100 % гарантии достоверности нет) : "Mozenrath was considered as a villain for the third film, but Disney wanted to distance it from the series. Brandis is also rumored to have been unavailable at the time. (It has also been stated in an interview that the character became less important when Williams signed to do the third film.) Because he was "replaced" by Cassim, Aladdin's father, some fans have speculated that Mozenrath and Aladdin were to discover they were brothers. This rumor reached such peaks that it is widely believed that Disney had actually intended to do this - however, it's all fan speculation. "
И пара ссылок: на аладдинцентрал и слова одного из создателей: