The general idea is that the boy doesn't feel that his father love or appreciate him very much. The father can be hostile or detached or absent or violent or a combination of those, but the main point is that the boy doesn't feel loved by his father, and so he doesn't see his father as a role model and he doesn't try to be like (mainly subconsciously). To the contrary, the boy is attached to the mother, see HER as a role model and learn and adapt to her model of the world - beliefs, values, emotional patterns, behaviors, manners etc. As a result he becomes effeminate at some level, starting from being very organized, gentle and to the point of talking , dressing and behaving in effeminate way. The subconscious craving for the father's love and acceptance causes the development of homosexual orientation, that is love and affection and appreciation from other men.
Because the mother gives much love to the boy, the father who's envy in the boy is hostile toward him and the boy senses it and also the mom expressing forbidding ideas and beliefs toward sex, aggression and masculinity and so, as a result of fearing the father and fear of losing the mother's love, the boy subconsciously suppress his heterosexuality.
All these things happen mostly subconsciously, it's not like a conscious decision. Sexual orientation is the result of psychological beliefs and patterns develops very early in a person childhood. That is as long as the person don't experience a substantially large amount of psychological damage in early life (mainly in childhood) , they'll develop the natural biological tendency which is heterosexuality - an act of reproduction and survival. Homosexuality is the result of psychological and emotional damage caused mainly by the relationships with the parents early in life.
*please reply objectively and not just by saying it's genetically determined and that's it.