Jesus answered with regard to the question: who sinned to cause the blindeness? Not the man, or his parents.
You can't take it any further than that, and say that none of them sinned ever.
No but you can read Joh:9:3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
I.e. = so God can look good. A quote that harks back to the Old Testament: Exodus 4:11 And the LORD said unto him, Who hath made man's mouth? or who maketh the dumb, or deaf, or the seeing, or the blind? have not I the LORD?
This is the move away from "sin makes you ill"... "OK, sin makes you children ill" (which failed as many bastards lived fine healthy lives) to more of a "God does everything."
In the miracle, God made him blind in anticipation of Jesus coming to earth and curing him and thus showing the power of God to blind and to make whole.
Personally, were I Yahweh, I would have not have played the individual, zero-sum game, but just cast a spell to cure everyone in the world of blindness. This would have been properly recorded and thus there would be proof of god.
Anyway, that story is one of the strangest episodes in the NT for many reasons. The more you read it, the more it becomes apparent that it never happened - some enthusiastic story teller wrote it. There was a lot of that about in those days.