Почему инструментальный падеж на этой сентенции?
Самым существенным отступлением пушкинских сказок от типа народной сказки была стихотворная форма.
I am not sure why "самым существенным отступлением" is in the instrumental case. If the translation is something like:
"The most significant deviation from typical folk tales in Pushkin's stories was in poetic form."
This is not a direct translation but I think that is the best I can do without it sounding awkward in English. I did notice that "стихотворная форма" is in the nominative, so I tried to place it near the beginning of the English translation, thinking that might shake loose something in my mind that would explain the instrumental case:
"Pushkin's stories' poetic form was their most significant deviation from typical folk tales."
But I am still at a loss. I feel like I get the general meaning, I am just not sure why, technically speaking, the instrumental is being used. Any help is appreciated. Thanks.
