First, their disposition did change after eating the fruit. They immediately felt fear, a novel emotion as far as the story was concerned. Their "eyes were also opened" (whatever that means), and they saw that they were ashamed at being naked and covered up (assuming this was contrast with not feeling ashamed from Gen 2:25).
The most dramatic change, I believe is that they also now had the knowledge of good and bad, so they lived into the world of judgment and "should have" and "ought to be." Previously not being moral agents, now they had a moral compass. Of course, that then begs the question, how could they have done what was wrong (disobeying) when they did not know right from wrong? A rock that falls off the table under gravity doesn't do something wrong even if you command it not to. God placed the fruit in reach and then placed a command and consequence which his creature had no tools to evaluate against their actions.
I love the question you are asking, but I think it's built upon misunderstanding this first part. Many approach the Bible as if it is a textbook for a system of ethics that is somehow objectively right and that we should follow. But the bible starts off saying that "ethical systems" are the poison that separate us from God and ends up with Jesus calling for non-judgment... This is not an ethics text, but a physics text. If you come at it with this hermeneutic, I think you'll see the Eden narrative in a totally different light.
Also, the serpent (nachash) was a beast of the field (we are told twice: Gen 3:1, Gen 3:14). Can we assume that the serpent (nachash) stood on legs at eye level, talking to the woman? There is a category of beings called "creeping things" in Genesis 1:25 which may have included serpents. But the Nachash was originally a beast of the field, it seems. So it would seem that being cast onto the ground to eat dust was a change in the same way that the consequences for Adam and Eve were changes. There are egyptian relics with images of serpents with legs and wings. There are also many snake species that still have a pelvis and vestigial leg stubs. Looking at a skeleton of a snake might have spurred such an origin story for the serpent on the ground without legs. For example, some pythons have leg stumps.
The serpent is described as "arum" (עָר֔וּם) in Genesis 3:1, and this sometimes gets translated as "crafty" or "sneaky." But arum is not a negative property. It is complex. For Example, in Proverbs 8:12, Lady Wisdom pitches her tent in/with arumah (the feminine form). It's really interesting to chase that word through the text. In the Septuagint, the word is φρονιμώτατος which also appears in the Gospel of Matthew 10:16. Jesus tells the disciples to be φρόνιμοι as serpents and pure as doves. This seems to be a valuable property which we are to emulate!
I think this Matthew 10:16 verse is fascinating. Trees reach their branches into the heavens (waters) above and their roots into the waters below. The trees were thought to be beings that traversed worlds. But serpents were seen to travel into the underworld when they went into their holes in the ground to hybernate in the winters and doves could ascend to and descend from heaven (as the spirit resides on Jesus). Oh, and this connection with the underworld was not a "bad" thing... That's Aristotelian moral cosmology, not Hebrew cosmology. Everyone went to Sheol down below.
There is a kind of dualism of groundedness and weightlessness in this statement.
Finally, note that the serpent (Nachash) is not a symbol of evil or violence, but of protection and even of God. Moses's staff became a Nachash to demonstrate the Lord's power. God sends fiery nachash in the desert to kill/punish the Hebrews and commands Moses to erect a bronze Nachash (serpent) on a pole in Numbers 21. Genesis 49:17 compares the tribe of Dan to a serpent (nachash) by the roadside to protect the Hebrew tribes. Heck, even John 3:14-16 compares Jesus to this serpent in Numbers, directly preceding the most quoted verse in the Bible. The egyptians had the ouroboros and the Uraeus as serpent symbols of eternal life and protection! The Rod of Asclepius is mythologically equivalent to Christ on the Cross and sits on the back of ambulances to this day.
That being said, I think there is also confusion about the serpent and the fruit of the knowledge of good and bad. Most authors have the serpent wrapped around the tree of the knowledge of good and bad when talking to the woman. But the serpent always represents eternal life and death and resurrection because it never seems to grow old, has no eye-lids or ears, and sheds its skin. In fact, serpents were thought to be immortal and in Gilgamesh, Hercules, and many other stories, were always associated with the eternal life principle. There are many parallels between this figure and the path that Jesus took. The knowledge of good and bad is for governing the world (see Solomon and 1 Kings 3:9), and eternal life is at right angles to that (hence the property for entering paradise in Deuteronomy 1:39).
Don't eat all the junkfood about serpents fed by the church. It keeps you away from understanding the text. That's is why I hang out here on Hermeneutics and not Christianity SE. So much less false baggage here.