The thing with Frozen is that it's focus was more in the misunderstood character rather than the Heroine. Most will assume Elsa is the heroine , but she is not , Anna is. And even so , Anna has more screentime than Elsa IIRC, but the film's focus was Elsa's insecurities and how you overcome those. The villian in Frozen was just an extra to make the plot spicier , and to have a happy ending. Either way , Anna was still going to end up with Kristoff so the prince whatever his name was , was just there.
Elsa is also more popular than Anna . Most people also feel the appeal of the songs Frozen has , particulary ''Let it Go'' , which it's understandable because they are catchy , beautiful and memorable , while also having a great message.
Old designs and concepts had Elsa looking like an evil witch and villian , but was abandoned in favor of a more human and vulnerable representation, which was a smart move.