Why is Rodrigo helping iago?

Rodrigo helps Iago primarily out of his infatuation with Desdemona, believing that by aligning with Iago, he can win her love and gain favor with her. Iago manipulates Rodrigo by exploiting his desires, convincing him that his schemes will ultimately lead to Desdemona's affection. Rodrigo's naivety and desperation for love blind him to Iago's true, malicious intentions. This alliance serves Iago's ulterior motives while further entangling Rodrigo in his deceitful plans.