What is the difference between the inclusion and exclusion of "kana" in phrases such as His, the Almighty’s, saying: (Indeed, Allah was ever Knowing, Wise) and (Indeed, Allah is Knowing, Wise)?

The phrase "كان عليماً حكيماً" (He was All-Knowing, All-Wise) is repeated eight times in the Holy Quran, while "عليماً حكيماً" (All-Knowing, All-Wise) appears fifteen times. The addition of "كان" (was) indicates the continuity and affirmation of the attribute. As for "إن الله عليماً حكيماً" (Indeed, Allah is All-Knowing, All-Wise) with the accusative ending, it is linguistically incorrect and does not exist in the Quran.