I've recently come across the sentence [花]{はな}さんの[車]{くるま}がほしいです, which I could intuit to mean "I want Hana's car". But Hana's car seems to be the object in this sentence.
Why is が used here instead of を?
I've recently come across the sentence [花]{はな}さんの[車]{くるま}がほしいです, which I could intuit to mean "I want Hana's car". But Hana's car seems to be the object in this sentence.
Why is が used here instead of を?
I think the problem comes from the translation of ほしい as 'want'. Although this is the most common translation, as you have pointed out, it breaks the grammar. ほしい is an adjective in Japanese and, as such, cannot take an object, so 'want' is rather clumsy as a direct translation.
If you want to preserve sensible grammar then it is better to think of ほしい as meaning 'is desirable (to me)'. This phrase naturally takes the thing that is desired as the subject of the sentence.
Of course when you translate from Japanese to natural English it is far more sensible to say "I want X" rather than "X is desirable to me" which is presumably why it is most commonly translated as 'want'.