Can someone objectively tell me why there are inconsistent creation stories in the book of Genesis?
Modern scholars mostly believe that the creation story in the first chapter of Genesis originated in a group of Jewish theologians known as the "P" (priestly) writers which would make it one of the latest writings found in the Old Testament even though editors would later place it first. These writings occurred some time after the 6th Century BC diaspora (When King Nebuchadnezzar of Babylon conquered Israel and drove the Jews out of Jerusalem into surrounding nations/areas.) The writing is part of a number of authoritative doctrinal statements setting down what orthodox Jews were to believe. These writings were an effort to keep the traditions pure and the story alive during a time when the Jews were scattered among many lands. The first chapter of Genesis underscores the Jewish belief that all that has ever existed, exists, or will exist comes from God.
The second creation story (Adam and Eve and the Garden of Eden) is generally attributed to a group of writers known as the "E" writers or those who used "Elohim" as the divine name for God. These were among the earliest manuscripts found in the Old Testament. The E writers were more interested in accounts of how "God" did things or how things came about and they probably originated the Jewish tradition of teaching via allegory, metaphor, and/or parables using real life or symbolic figures. The story of Adam and Eve and their progeny is the first description of the reoccuring Old Testament motif of creation, sin (spoiling God's creation), judgment (consequences of sin), redemption (salvaging sinful humankind and setting it forth again in the story of the People of God.)
The stories are inconsistent because they were written by different people who lived as much as 1000 years apart and who were writing from entirely differenent perspectives for different reasons. I believe both were intended to be read as symoblic or allegory rather than literally, but there are many who would disagree with me about that.