Complex sentence: He tries to figure out why he hates him so much, after playing a Why-do-I-hate-him game with Carla, he sees Ed refusing the case study, finally realizing that he hates him because he is lazy.
Split into simpler sentences: He tries to figure out why he hates him so much by playing the Why-do-I-hate-him game with Carla. He sees Ed refusing the case study, and finally realizes that he hates Ed because he is lazy.