Better question, why arent you converting to Judaism, since they had 2/3 of the Bible first, according to your thought process??? Hmmmmmm?
Because I believe Jesus is the promised Messiah so I can't be Jewish.
It's easy to say "Christians had [the Bible from the beginning of Christianity]" but that's not very helpful to me. Not then (when I first believed) or now, because a lot of people call themselves Christian today but believe a lot of different things.
“Because I believe Jesus is the promised Messiah so I can’t be Jewish. “
Plenty of Jews believe Jesus is Messiah.