All of the elements in Indian, Buddhist, and Eastern philosophy made their way into German pre-Christian mythology. It was also absorbed by Greek and Roman cultures. Indeed, these ancient elements run through all cultures and can be traced at least as far back as the Sumerians of the Near East.
They have been trivialized as "fairy tales" or intellectualized as archetypes and been made to symbolize facts that have been simplified by weaving them into personified tales with comprehensible human-like motives. The great epics of Sumer such as Gilgamesh, the Vedas, Greek and Roman lore all harken back to stories known to all humanity but each adapted to particular cultures.
While the Buddha recognized these elements -- and spoke of them frequently to form what was later standardized as Buddhist cosmology -- he was not the first to be aware of them. He spoke of the things (worlds, inhabitants) familiar to ancient Indians and explained those things not familiar to them -- namely, how those worlds came to be, the karma leading to rebirth in those realms, and liberation from the entire round of discontent (dukkha) in incessant rebirth. Wagner immortalized these Pagan stories in opera as the Ring Cycle.