Why do Jews (or anyone for that matter) need to accept the trinity?

Yahweh - the god of abraham, isaac, and jacob. - is still their god. Same god as Christians.

Men like Abraham were declared righteous before Jesus and presumably found some sort of salvation or grace. Elijah went straight up to heaven without dying even.

Why does one need to know and accept the metaphysics of the godhead as a requirement for eternal life?

It's strange to call people unbelievers or heretics simply because they can't accept the middle platonist construct theologians centuries after Jesus died made.

It’s like pass this metaphysics exam or burn.

When the thief on the cross got in by saying "jesus, remember me in your kingdom".

And if you want to get really deep with it, maybe yahweh isn't JUST the god of israel. Maybe other nations worshiped the same god under a different name. The hebrews had a dozen different names for him of their own.