About the series finale, I read something about it and made me realize why the villainous trio got their fate. Back when they were initially defeated, they didn’t want to be redeemed because they were so far down into their villainous ways that any attempt to turn them good would’ve been moot. Tirek likely would’ve said no, Chrysalis slapped Starlight’s hoof and bolted out of there and Cozy wasn’t even remorseful for her actions while trapped in Tartarus and stayed her usual self. After they were defeated a second time, what were they gonna do? Suddenly act all remorseful and apologize to everyone for stealing magic from some ancient bell, destroy the capital and almost caused another ice age? That would’ve been such a sudden and jarring change to their character, since they got dealt with that hand with Starlight and that went very well so they didn’t want to repeat the same mistake. I’d say that they played their cards right there because having them be suddenly redeemed would’ve been unrealistic and having them escape again would mean that they would try again eventually or at best just become a minor nuisance. I get that the show is called “Friendship Is Magic” and redeption is it’s MO, but it can be a double-edged sword and seeing as how the past couple of redemptions were spotty at best, doing it again to them would’ve had the same results.
That and everyone has their limits, including Twilight Sparkle. There is only so much that the Princesses would’ve tried and done everything before they reached their limit and deemed them a lost cause, we all go through that or have been through that at one point in our lives. Maybe things would’ve played out differently if the series would’ve continued on and they did get redeemed, but I think it would’ve been too close of a parallel to Starlight and Sunset for it to have really worked.