Look back at Genesis 3 and the Fall- as the old joke puts it "Adam blamed Eve, Eve blamed the serpent and the serpent didn't have a leg to stand on"
One major consequence is that Adam and Eve were expelled from the Garden of Eden.
And this is my random thought- wouldn't it have been simpler if God had expelled the serpent from the Garden of Eden? Send the serpent away so he couldn't tempt Adam and Eve and the incident with the tree could be dismissed as a one-off and then everything in the garden's lovely? Have God say a "Sorry humans, shouldn't have let the serpent in. Won't let it happen again"
So, why didn't He? Ultimately to sin is a choice. Adam made that choice, Eve made that choice, we all make that choice. Satan may tempt, may whisper, may encourage, but ultimately, you are the one who makes the choice. Sometimes, a Christian's bad behaviour gets dismissed as being down to the devil. Sounds a bit spiritual, but that simply excuses the behaviour.
And to be blunt, that ignores the Cross. If sin is no more than Christians acting out of character due to the devil, rather than being our own fault, then why do we need a Saviour?