When it comes to this question, the first thing to remember about Cyrano is that he is not comfortable in his own skin. Though he possesses a lot of wonderful qualities, including great humor, artistic talent, and quick cognition, he has negative thoughts that he keeps to himself. Mainly, he is insecure about his large nose. He sees his strange appearance as an obstacle for him to attain a loving partner.
Let’s now contrast Cyrano to Montfleury. The overweight Montfleury is not much better in the looks department. In addition, Cyrano detests his a terrible acting skills. It is true that Cyrano's affection for Roxane made him want to keep Roxane away from Montfleury. However, his feelings are not entirely selfish. Roxane is a truly outstanding woman, in every way, so Cyrano does not believe that he or Montfleury are truly worthy of her affection. On the other hand, Cyrano does assist Baron Christian de Neuvillette in his pursuit of Roxane because Christian is an upright individual. He does not have Cyrano’s intellect, but he is noble and earns Cyrano’s respect. The events of the play prove that Cyrano is capable of putting his feelings aside to help the people he loves.
There are two reasons for Cyrano's hatred of Montfleury.
The reason Cyrano states is that he hates Montfleury because he is a terrible actor. He chases him off the stage after ridiculing him for being fat and banishes him from the stage for a month.
The true reason that Cyrano hates him is one he keeps from others. The reason is that Cyrano is in love with Roxanne. Montfleury made a pass at her and this infuriates Cyrano. Cyrano is insanely jealous and want s to keep him away from Roxanne.
cyrano claims its because he is a bad actor, but later we find out it is because Montfleury made "goo goo" eyes at Roxane during one of his plays.