Siddhis are a reality, and the science behind them has been passed down from time immemorial by the rishis and preserved in the Vedic texts. In actuality nothing is mystic. Everything functions according to natural laws. The rishis, by virtue of their expanded consciousness, understood the functioning of matter on the subtle levels of sound and mind. They actually understood the absolute laws of nature, and not just the surfacial reactions caused by mixing gross physical elements.
True transcendentalists have no interest in mundane material life.
As such, the rishis did not give much importance to material powers and perfections. They were not interested in acquiring wealth, power, fame, etc. Their aim was much higher. But, ceasing such engagements by experiencing a higher taste, he is fixed in consciousness. That is the brahmananda, paramananda, shivananda, yogananda spoken of in the scriptures - the spiritual bliss which is the constitutional nature of the self.