They’re changing her now because they screwed up her character royally in season 1, and now they’re bringing her back, not in flashbacks, but as a villain. They need her to be a formidable villain, which her season 1 persona didn’t quite imbue. She is supposed to be the ‘mistress of all evil’ who has ‘all the powers of hell’, a power grade which was significantly down-graded in OUAT. A frizzy-blonde haired, purple frills wearing lady, who we’ve already seen losing to Regina once (because of her love for a pet unicorn!!!), does not a formidable villainess make. Why are they changing her now? Because they need her to be a villain, not a brony.
Royally screwed up says you, new and interesting interpretation (which was the point of the show) says I. She was formidable. The woman could turn into a dragon and created that booming voice in WL. And…do you not get that the reason why she lost to Regina over her love for a pet unicorn was because Charming put TL-egg inside her? That changed her. And, of course the powers were less than Regina…Regina was the main character who needed to cast the curse. You cant’ have Regina loosing when 10 mins after the fact she needs to be casting the curse that was the whole premise of the show.