It wasn't just a momentary decision to ignore Hinduism that let to his enlightenment, but a deliberate practice of self examination.

Buddhism is actually a kind of psychology, a study of the mind, and the historical Buddha studied his mind methodically for years using introspective techniques (meditation) that he adapted from Hinduism.

But it's also more than that. Just like you can't learn a difficult skill like hitting a baseball by looking at pictures of others doing it, or by thinking about it or by being told how it feels to do so, you can't realize enlightenment without striving for it.

So buddhism is a set of teachings about the nature of your mind, combined with practices to help you fully realize (come to know) the truth of these teachings in your own mind and body.