I loved the show and I thought Tonya's acting was excellent. However, her voice was shaky throughout the majority of the show starting with a severe and starting crack in the opening line. It made it very difficult to concentrate on the show because it happened so frequently and at times would affect my ability to understand the lyrics (this was before the cast recording was released). I think that may have had some part in the voters' decisions, but I think there was another factor as well. The character of Caroline simply does not have much emotional range. She's pretty much angry and bitter from beginning to end with very little change. She has the wonderful Lot's Wife to express her moment of epiphany, which is...angry and bitter, just louder.
When examining the performances of Idina and Tonya as well as their music and the characters they performed, in the end, I have to agree with the Tony voters. Though I know it's not politically correct to acknowledge the enjoyment of anything having to do with Wicked, I have to admit Idina's performance was electrifying, engaging, humorous and touching. The night I saw Wicked, both she and Chenoweth gave flawless performances. Tonya did not. Sad, but true.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian