Why does my code works?

Yes, look at this:

                 float spreadX = Random.Range(-weaponSO.spread / 100, weaponSO.spread / 100);
                 float spreadY = Random.Range(-weaponSO.spread / 100, weaponSO.spread / 100);
 
                 Vector3 direction = originPoint.TransformDirection(spreadX, spreadY, 1);
 
                 if (Physics.Raycast(originPoint.transform.position, direction, out RaycastHit raycastHit, weaponSO.range))
                 {
                     direction = raycastHit.point - GameObject.Find("Muzzle").transform.position;
                     GameObject projectile = Instantiate(weaponSO.projectilePrefab, GameObject.Find("Muzzle").transform.position, Quaternion.identity);
                     projectile.transform.forward = direction;
                     projectile.GetComponent<Rigidbody>().AddForce(direction.normalized * weaponSO.projectileSpeed, ForceMode.Impulse);
                     projectile.GetComponent<Rigidbody>().AddForce(originPoint.transform.up * weaponSO.projectileUpwardSpeed, ForceMode.Impulse);
 
                 }
                 else
                 {
                     direction = GameObject.Find("Muzzle").transform.forward;
                     GameObject projectile = Instantiate(weaponSO.projectilePrefab, GameObject.Find("Muzzle").transform.position, Quaternion.identity);
                     projectile.transform.forward = direction;
                     projectile.GetComponent<Rigidbody>().AddForce(direction.normalized * weaponSO.projectileSpeed, ForceMode.Impulse);
                     projectile.GetComponent<Rigidbody>().AddForce(originPoint.transform.up * weaponSO.projectileUpwardSpeed, ForceMode.Impulse);
                 }

My question is, why does the spread still works once I define the new direction inside the raycast?

Thing is, i first pass the direction with the spread on

                 float spreadX = Random.Range(-weaponSO.spread / 100, weaponSO.spread / 100);
                 float spreadY = Random.Range(-weaponSO.spread / 100, weaponSO.spread / 100);
 
                 Vector3 direction = originPoint.TransformDirection(spreadX, spreadY, 1);

then, because I can shoot the sky, i define the new direction if I hit a collider here

                 if (Physics.Raycast(originPoint.transform.position, direction, out RaycastHit raycastHit, weaponSO.range))
                 {
                     direction = raycastHit.point - GameObject.Find("Muzzle").transform.position;
                     GameObject projectile = Instantiate(weaponSO.projectilePrefab, GameObject.Find("Muzzle").transform.position, Quaternion.identity);
                     projectile.transform.forward = direction;
                     projectile.GetComponent<Rigidbody>().AddForce(direction.normalized * weaponSO.projectileSpeed, ForceMode.Impulse);
                     projectile.GetComponent<Rigidbody>().AddForce(originPoint.transform.up * weaponSO.projectileUpwardSpeed, ForceMode.Impulse);
 
                 }

But the spread still works??????

The next lines are just to spawn the projectile on the muzzlelocation;

             else
             {
                 direction = GameObject.Find("Muzzle").transform.forward;
                 GameObject projectile = Instantiate(weaponSO.projectilePrefab, GameObject.Find("Muzzle").transform.position, Quaternion.identity);
                 projectile.transform.forward = direction;
                 projectile.GetComponent<Rigidbody>().AddForce(direction.normalized * weaponSO.projectileSpeed, ForceMode.Impulse);
                 projectile.GetComponent<Rigidbody>().AddForce(originPoint.transform.up * weaponSO.projectileUpwardSpeed, ForceMode.Impulse);

But I don't understand why if I shot a wall, the projectile will go exactly where my aim is but still respect the spread defined outside the raycast???

I did this sort of on a whim, because for some reason my spread was only working on one axis if I looked in a certain direction, but perfectly well if I looked in the positive or negative Z axis, so the "originPoint.TransformDirection" was the only thing that worked.

I want to understand my code.