Even fundamentalist Hindus do not claim it existed before 2000 BCE. Most likely no more than 1000 BCE from archaeological evidence.
That makes the birth of Gautama Buddha only about 400 years after Kassapa Buddha. Is this a correct assumption?
If yes, are Buddhas born every few centuries and might it be that they were born in such a location (say, Caucasian region in 500 CE) that the teachings did not survive for more than a century?
I know it is idle speculation that does not help practice .. but the mere thought that it may have happened is exhilarating.Not long after Jotipāla’s ordination, a fortnight later, the Buddha Kassapa—having stayed in Vebhaliṅga as long as he wished—set out for Benares. Traveling stage by stage, he arrived at Benares, where he stayed near Benares, in the deer park at Isipatana.
https://suttacentral.net/mn81/en/sujato