"Buddhists" are mentioned in the far future in multiple places like the Kalki and Bhavishya Puranas. This is over 400,000 years in the future for the Kalki Purana, so they can't be Buddhists as we know them.
Anyway, does scripture or any guru given an explanation for why Buddhism lasts so much longer than the other non-Hindu faiths, who don't appear as a faith practiced?
You make the mistake of equating a Buddha with Buddhist. The Buddha of our time did not create Buddhism - Buddhism was created by his followers. The word "Buddha" is simply a Sanskrit word that means Awakened or Enlightened.
In Sanskrit, names always only represent the properties which the object/Being possesses. Because of this, every incarnation of Vishnu, Shiva, etc - would all by definition classify as Buddhas, although they are definitely greater than just a simple Buddha. So for someone to be labeled Buddha, it is a statement that they are enlightened/awakened. That's just what the word means.
Likewise this is the reason many people consider Gautama Buddha to have been an incarnation of Vishnu. However again do note that Buddha != Buddhist. Buddhism was created by Gautama's followers, Buddha himself didn't have a significant role in developing what is called Buddhism today - rather his followers wrote down what he spoke.
Naturally because none of his followers are Buddhas themselves, the teachings inevitably become distorted overtime - this is inevitable because formal "Buddhas" only come into the world to restore the teachings. For example consider the modern buddhist idea of "no self" - the Buddha never taught any such idea, rather he only taught what the self isn't, and even explicitly stated that after all those non-self properties are eliminated, there remains a transcendental awareness.
So, contrary to popular belief, Buddha himself really didn't contradict Hinduism much at all, rather that blame is on his followers and the general decline of the dharma overtime. It's also important to remember that during the time of the Buddha, there was no such thing as "Hinduism", rather there were just the Vedic texts and practices. The primary opposition Buddha had was against the animal sacrifices, which we know arose in the Treta Yuga due to the decline of righteousness and knowledge. All incarnations of Vishnu would be against animal sacrifices by His very nature due to the fact that it represents a lowly practice that arose from loss of knowledge.
Basically there's no problem with Buddha's themselves, only with followers that distort the teachings. The word Buddha is simply a Vedic Sanskrit word that means awakened/enlightened one.
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