Saya menghormati Otaku.

Saya menghormati Otaku.
Pasalnya (Karena), mereka mempunyai (Keinginan yang kuat) banyak nafsu.

*You can use "Karena" to make it sounds more natural. Using "Pasalnya" is a way much formal :)

*"Strong passion" literally translated as "Keinginan yang kuat" even if you try to translate the word "keinginan" will be translated as "desire". The word "yang" can be translated as の-particle in Japanese. for example: 強いの情熱.

The world "nafsu" in Indonesian sounds a bit negative because it will be translated as "lust" in English

Mereka berupaya(/berusaha) (yang terbaik) untuk (kegemaran mereka) hal favorit.

*the words "Try to do" can be translated both "berupaya" or "berusaha", "berupaya" sounds more formal. "best" literally translated as "terbaik" or "Ichiban" in Japanese. 

*The words "kegemaran mereka" means things that they like or favorited. 

(I respect Otaku.
Because, thy have strong passion.
They try to do thier best for their favorite things.)

Honestly, your Indonesian is very good! I'm surprised!

Semangat belajar Bahasa Indonesianya ya! インドネシア語を勉強がんばってくださいね。