I’m betting Eva finds out about Cora’s deception and using dark magic and that’s why Cora and Henry Sr. lose everything.
Love this idea. Young Eva seems like she may have been the type to take great pleasure in exposing Cora’s deeds, and perhaps that led to Cora and Henry being completely excommunicated. That right there would be plenty of motivation for Cora to kill Eva and set up Regina to become royalty.
Would take away all her power and since that is all that matters she would defiantly have all reason to ruin everything in Eva’s life that matters to her