Yes, Gautama Siddhartha Shakyamuni sat on his own before being known as the Buddha. But this was after many years of practicing with teachers in community. His first teacher was Alara Kalama, who eventually asked Gautama to co-teach with him. But Alara Kalama’s teaching did not resolve Gautama’s deep questions. So he left and practiced with another teacher, Uddaka, who also eventually asked Gautama to co-teach with him. But again, Gautama’s deep questions were not resolved. It was only after many years of practice in communities of renunciates headed by recognized teachers who both acknowledged the maturity of his practice that Gautama went off on his own.
There are good reasons for this. Without community our practice can very subtly reinforce our sense of self and reinforce our karmic habits. Without guidance from people who have deep experience with practice our opinions can seduce us into thinking we have understanding. As for what this question calls religious trappings, these are simply practice forms that arose in order to provide a container for our practice, a container that is not dependent on our personal likes or dislikes, our opinions, or our ideas. The ones that have stuck around are the ones that people have found useful. In Buddhism these are called expedient means, and it is said that there are 84,000 expedient means. This means that there is a wide variety of forms and a wide variety of communities in which to practice — if one doesn’t happen to fit you, you can probably find another one that does.