Err... source?
If you are interested in investigating, It'd be illuminating to contrast the belief systems in Vedas and Puranas. (Rigveda and Puranas to be more specific. ) If my memory serves right, Narayana(Vishnu) was a minor diety in Rigveda whose only claim to fame was carrying Indra on his back to circumnavigate the universe 108 times. He gradually started gaining more prominence as time passed, as a benevolent and sophisticated alternative to replace the more belligerent/primitive Indra. By mid 15th century(I could be wrong), this process was complete, with Vishnu taking over Indra completely, as established in that Govardhanagiri tale where Indra was utterly humiliated by Krishna.
Coming to the claims on Buddhism, once again, examining the Rigvedic and post Rigvedic belief systems can help you hypothesize how things unravelled. (Replacement of Horse with Cow as the sacred animal, renouncement of non vegetarianism, incorporation of Tantric belief systems etc ) Destruction of Buddhist monasteries and massacring the monks is quite well documented too. Read about Pushyamitra Sunga for example.
Edit: Typos
Can you be more specific about what things you feel science cannot address? It seems like the one and only proven method for understanding our universe.
I mean, we understand relativity well enough to predict astronomical movements and to account for it when synchronizing GPS, we understand biology well enough for genetic engineering and complex medicine, chemistry well enough to create exotic materials and superconductors, quantum mechanics enough to harness it for computation, physics enough to split the atom, space travel, astronomy, etc. We understand a lot more than "the most basic things."