You keep stating your opinion as it it were fact. lol.
Because I don't believe in sacred manifestations, there is nothing to prove. Certainly the later 3 'manifestations' you mention (I would call them historical personalities, and one I'm not sure existed) have proved they were capable of causing a lot of mischief, I suppose, yes?
You and I won't be around in the same ego/personality of this lifetime. Look at ancient civilisations like the Romans, the Greeks, the Egyptians, and others. Where are they now?
But then ... oh yeah, those darn Hindus, for some reason, (hint, it isn't manifestations) they're still around, just as relevant as they were 4000+ years ago, despite several nasty invasions or attempted genocides. Pesky guys just won't go away, much like on this thread, lol.
it's a privilege having Hindus around generating ahimsa as it makes this world a much better place.
I believe the Manifestations were perfect Beings Who each came with a specific mission to help humanity spiritually at the time they appeared.