Siddhartha Gautama, the Buddha as he is known, was an aristocrat by birth and his teachings are, by their nature, only attainable by those removed from the necessity of working for a living.

As to the Yeshu'as, one was an Essene from Galilee teaching a reformed Judaism. He was a hothead and a troublemaker, so the Sanhedrin sent an agent called Yehudah to bribe him with thirty pieces of silver to get out of Jerusalem. He and his family then either went to Alexandria in Egypt or to Massilia (Marseilles) and lived happily ever after. The other Yeshu'a was a Judaean aristocrat who claimed descent from both King David and the Maccabees, became a Zealot terrorist and was captured by the Romans and crucified. Most o Christianity was made up by the Hellenised Jew known as Paul, who dreamed up a new mystery cult with the aim of making lots of money by charging for initiation.

Isaiah is a book of prophecies and no more to be relied upon that that of Nostradamus. Except, perhaps, as a warning to stay away from mouldy rye and those funny-looking mushrooms!

The Bhagavad-Gita, like the teachings of Buddha, is a rareified text for the perusal of those with the leisure and education to follow its arguments and precepts. Meaningless to the ordinary people, wo had work to do. Work serving those with the leisure to read.

Please bear in mind that all sacred texts share the following characteristics:

They are all much more recent in origin than their devotees claim.

They are all of dubious and multiple authorship.

They have all been, at various times, redacted, curated, edited, amended and added to in accordance with political agendas.

They are not trustworthy, and some are not even coherent.