So, by your reasoning, Adam and Eve, both created by God, raised themselves up by eating of the Tree of Knowledge and God decided to kick them out of the garden because they might eat of the Tree of Life and live forever. Now that they knew good from evil, could not God just have given them a command to not eat of the Tree of Life? And if they did, God being their Creator, could kill them in punishment, yes? Why, in following your logic, would God be forced to expel them from the garden?
If Eternal God, without beginning or end, created a creature who could eat the fruit of a tree He created and become like God, would that mean that God is NOT God but simply a great magician? God has no beginning or end; He was not created. Yet, by your logic, He created creatures who could become like Him but He has no beginning so He could not have created such creatures and they could not become like Him.
If you depend on everything written in the Bible as the ONLY direction from God, you would hold the partial truth as many of our wayward brothers and sisters do today. I’m not saying Catholics have ALL the truth but we are closer because we have Tradition and the Magisterium that’s been pondering these very issues for over 2,000 years. While there is no statement why they were ejected from the garden, we can see from other examples in the Bible where people disobey God and are punished.