I’ve never understood this concept of inheritance. It seems completely bogus.
It makes much more sense that Adam sinned because he was of mortal flesh from the very beginning.
Sin did not turn Adam mortal… Sin got him partitioned from the Tree of Life. Does God say that eating of the Tree of Life would be futile for Adam? No. In fact, the Tree of Life is still so capable of keeping Adam alive forever, God has to set up an angel and a flaming sword!
Humanity, like Adam, must atone for sin - - because it is the normal state of being for mortal flesh.