one of my favorite parts of wicked is watching elphaba's idealism and glinda's realism clash. and before anyone says anything, yes glinda is the realist between them. she sang an entire song about it. it just goes over ppl's heads coz they dress it up in bubblegum pink and a jaunty tune.
elphaba is the idealist. she has dreams of how Oz could be a better place, where everyone is accepted for who they are and aren't opressed or marginalized. she becomes a revolutionary because of those values, because she believes in fighting for the rights of freedom and the future.
and the other side of the coin is glinda, who understands innately how the world works. it's not about how much knowledge you have or how good you are at what you do. you can be the most qualified person for the position but if you're not popular with the masses, you're done for.
and those values they each have are constantly clashing with each other. elphaba believes she can fix the system from the outside. glinda believes she can play the long game and fix it from within. they both believe what they're doing is the best way to protect.
they don't see the other's POV until For Good. it's only then when elphie understands that the way she's been viewed has backed her into a corner and hurt her cause. it's only then does glinda choose to believe that the world could be a better place, that if she told the truth, nothing will happen because there must be goodness in the world. and by then, well, by then there isn't much of the song left. it's been written. all they can do is sing.