This is not implying that all of a sudden they have this new found power and that before they did not know what was good and what was bad. They themselves already had the power to discern between something that was good and something that was bad they had a counciessnes and had free will and thinking since they were created imaged after God.(2 Corinthians 3:18) I mean eve herself refuted Satan the first time knowing it was something that God condemned doing. What it is saying here is that like God,  they have acquired "knowledge" to Judge themselves what was good and what was bad.(Jer 10:23 ~it does not belong to men to walk thier own step~)By disobeying God they are now judging themselves what they deem good and what is bad, disrespectfully putting thier judgement of what is good and bad over the Judgement of God.
Just an extra note lol.  Not everytime the bible talks about knowledge does it place that word in good light as it talks about an erroneous knowledge and a correct knowledge which is that of God. (1Ti 6:20, 2Pe 1:5, 2Ti 3:6, 7Col 1:9, Eph 1:15-17; Php 1:9, 1Ti 2:3, 4, Col 3:10, 2Pe 1:2.~ verses that about how theres an incorrect knowledge and that talk about accurate knowledge implying theres a wrong one)


Something you may ask yourself lol: If this isn't a new found power? Why does it say that they opened thier eyes and realized they were ****? Almost as if this new power told them that being **** was wrong. I asked myself this too when reading this haha~ anyway 

It said that once they ate the fruit, thier eyes opened and they realized they were ****. If you think that they now have this new power of knowing what was good and bad. This implies that, that knowledge told them that being **** is bad. Is being **** a bad thing? You see this can be explained as it is actually is expressing that they started to be eat up by thier  counciessness and now becuase they have sinned, they do not see their body as holy and well belived that covering thier sinfull body both w made up nature garments and litteraly hiding, since they were ashamed that God would see them like this. One can see this as directly after God asked them why they thought they were ****, he followed it up by questioning them if they had ate from the forbidden fruit. Before they ate the fruit God did not tell them they were ****, or that they should cover up, well it was not until after they sinned that God himself made them clothes himself as once again its to prove that thier body is unholy now as they have sinned.


In addition to this eve told God that the serpent decived her. If what the serpent said was true, why would she say she was decieved. Maybe just like you and me who at first thought this was a actuall power of finnaly knowing what was good and bad and that they did not know at first, Maybe  Eve thought she was also gaining a power and thats how she was decieved.