Yes, she was a breakout star, casual fans liked her, her own following grew and writers loved writing her which is why she was suddenly everywhere. That's also why the idea of her 'being better as a villain' is ridiculous and likely pushed for by trolls since she only gained prominence (and a considerable fandom) when she became a hero (well anti-hero in my opinion, but that's a whole other topic).
Oh and as for the Scemme being the reason she was popular, most people disliked the pairing, so I'm not sure what your point is here. The death of Jean and the sidelining of Xavier contributed to her getting so much spotlight, sure. But she still got it and because popular because of it.
Most iconic member of the 21st Century? Probably not. No one is really arguing that anyway, but iconic nonetheless and had an important role to play in most iconic stories since. For better or worse. *sighs in IvX*.