“Original sin, therefore, seems to be a hereditary depravity and corruption of our nature, diffused into all parts of the soul, which first makes us liable to God's wrath, then also brings forth in us those works which Scripture calls "works of the flesh" (Gal 5:19). And that is properly what Paul often calls sin. The works that come forth from it – such as adulteries, fornications, thefts, hatreds, murders, carousings – he accordingly calls "fruits of sin" (Gal 5:19–21), although they are also commonly called "sins" in Scripture, and even by Paul himself.” Link.
He had to be subject to the Fall so he could become mortal like us, and die for our sins. The fall of Adam had brought death into the world and made us all mortal. If he had not been subject to the fall of Adam he would have been immortal as Adam was before the Fall, and he could not have died for our sins. He had to become subject to the Fall so that he could overcome it on our behalf. It is because of his death and resurrection that we overcome death and are able to live again. It is his resurrection that makes our resurrection possible.
If Jesus had not been made subject to the consequences of the Fall he could not have died, been resurrected, or atoned for the sins of the world. Being made subject to the consequences of the Fall does not automatically make anybody a sinner. It is yielding to temptation that makes one a sinner.