Breakdown of Вы путаете факты: каким именно был его мотив?
он
he / it (for a masculine noun) / it (for a neuter noun)
вы
you (plural)
какой
which/what kind of (m, sister forms: какая, какое)
быть
to be
Questions & Answers about Вы путаете факты: каким именно был его мотив?
Why is каким in the instrumental case here?
In Russian, the predicate after the past tense of быть (like был) usually takes the instrumental case to describe a state or characteristic. Here, the question word какой (what kind of / which) becomes каким to match that rule.
Could I use как раз instead of именно in this sentence?
No, you can only use именно here. When you want to add "exactly" or "specifically" to a question word (like who, what, where), you must use именно. The particle как раз means "just the right amount" or "as it happens," and it is not used to emphasize question words.
Why does именно come right after каким? Can I change the word order?
When emphasizing a question word, именно almost always comes immediately after it (кто именно, где именно, каким именно). Putting it before the question word or at the end of the sentence would sound unnatural to a native speaker.
I know путать means "to confuse". Can I use it to say "I am confused"?