Why is there Hindu gods in this decorated wall in the Vihara of Bhaja

I am a student of art and I am studying on Buddhist art .In the Vihara of Bhaja there is a decorated wall with two important gods of Hindusim, namely Surya and Indra. It refers to the Shunga period. - Why they have used images from Hindu gods? - Why would they have made this kind of art at all? I thought that Buddha was against Hindu gods, and that people should follow him because Buddha advised that people should rely on themselves and not on the gods!