But why is it part of human nature? If God is omni-etc. and created humans, why include the evil then punish us for it? God is capable, certainly, if God is omnipotent and omniscient. By not doing so, God cannot be omnibenevolent. And, if omnibenevolent, then God is either not aware, or God' power to intervene is lacking.
You will only ever get the biblical view from me.
The Bible says sin became part of human nature because of Adam and Eve's sin. You must have heard of original sin. Sin is in our 'genes'.
We also believe we cannot tell God what or what not to do because He is sovereign. He has the right and the freedom to do whatsoever He pleases, whenever He pleases, however, He pleases, in respect to whomever He pleases.
Do I understand it? No. Do I struggle with that? For sure.
In theology, it is called the theodicy problem - why a perfectly good, almighty, and all-knowing God permits evil.
I don't know the answers but that is how it is. I look forward to the new heaven and new earth where all pain and suffering will be no more. For now, we're not in heaven yet.