A followup to this piece and possible in-universe explanation as to how friendship and magic have disappeared from Equestria at the start of Generation 5. Based on a scene from Blade Runner 2049.
 
L: “Flurry was… consumed with jealousy that I was Princess Twilight’s prized pupil. The successor to the throne of friendship. It ate away at her. Bitterness and rage consumed her.”
 
S: “Wait, Princess Flurry Heart?? Of the Crystal Empire? But all the stories and the legends always said she was joyful, loving, compassionate, even ‘til her untimely death… Nothing ever mentioned anything of this spite or hatred.”
 
L: “It’s all true up until the very end. See, the end… I omitted it. I couldn’t stand to let my best friend’s legacy be that of her descent into malice. Looking back, it may have been my own cowardice, or my unwillingness to truly accept what had happened. But that’s why no one has ever heard of what I’m telling you now. It’s not in any archive, nor any book, scroll, or tapestry. I’m the only one who knows.”
 
S: “You mean to tell me that she was jealous that you were the new princess of friendship and not her? I don’t understand… According to everything written by Princess Twilight Sparkle, friendship was thriving! How could everything just fall apart like that?”
 
L: “Even when Flurry was born, her magic was unlike anything Equestria had witnessed. No one had ever heard of somepony being born an alicorn. She had so much raw ability and talent, there was no telling what she could have accomplished with it. Flurry had both the Sparkle bloodline and the Cadenza bloodline flowing through her. The sheer power that she possessed was unfathomable, it blew away her teachers, her parents, and even Princess Celestia herself.”
 
S: “Princess Celestia… The one who came before… You knew her?”
 
L: “No. Not personally. All I knew is she was the mentor of my mentor. The point is, Flurry had the capability of influencing the entirety of Equestria, and her mother had hoped to be able to use this as a force for good. A beacon of light, hope, and friendship in the world. By the time I had realized what she was going through and how she felt towards me, it was too late. My best friend hated me for what I took away from her. What started as a mere twinge of envy grew like wildfire until it became an inferno of fury and desire. I didn’t see it or couldn’t recognize it. Maybe because I was so preoccupied or so blinded by my own sense of self-accomplishment… Doesn’t matter. I was supposed to be the Princess of Friendship, but I couldn’t even save my best friend. At least, I thought I couldn’t. And therein lies my mistake.”
 
S: “What happened after that? Princess Luster Dawn, what did you do?”
 
L: “I did what I thought I had to. She confronted me right before my coronation and made it clear that only one of us was going to walk away alive. Looking back now, I… I should have tried harder to save her, tried with everything I had to stop her even if it cost me my life… Tried ANYTHING ELSE than what I did…”
 
S: “…”
 
L: “I killed her. I was the one who killed Princess Flurry Heart. I didn’t know it at the time, but when she died, her agony and anger rolled over Equestria, slowly poisoning everyone with her negative energy. What had once been Equestria’s young beacon of love was now an unstoppable torrent of hatred. I could not live with my own failure, so… I lied. I told everyone I found Flurry’s body.”
 
S: “And Equestria mourned her… though her cause of death was never determined.”
 
L: “That’s right. After her funeral, I was coronated, and I became the new Princess of Friendship. The last Princess of Friendship. Little did I know that my mistake had not only cost me my best friend, but all of Equestria the magic of friendship. By the time I realized all those years later the consequences of what I had done… it was too late. The damage had been done. My reign was fruitless and meaningless, so in my shame, I came here to exile.”
 
S: “Until I found you.”
 
L: “You found me all right. I bet you wish you hadn’t. But at least now someone knows the truth. What happened to Equestria? Well… I killed it. I was the one who brought about the end of friendship.”