Unity2D I can't change the TrailRenderer material of a cloned object

In the game I'm making, I clone a Ball object whenever a "split ball" power-up is acquired. Everything works as intended except the TrailRenderer material. The Ball prefab has a default material used for TrailRenderer in the beginning. This, however, changes when the ball hits an object controlled by the player (which is called a "bumper"). The material changes work perfectly on collision. Here is the shortened script for the Ball object:

[NonSerialized]
public TrailRenderer trailRenderer;

[SerializeField]
private Material defaultTrailMaterial;


void Start()
{
    trailRenderer = GetComponent<TrailRenderer>();
    trailRenderer.material = defaultTrailMaterial;
}

private void OnCollisionEnter2D(Collision2D collision)
{
    if (CollidedObjectIsABumper(collision))
    {
        // SetTrailColorToBumperColor() is called along other calculations
    }
}

private bool CollidedObjectIsABumper(Collision2D collision)
{
    return collision.gameObject.CompareTag("Bumper");
}

private void SetTrailColorToBumperColor()
{
    trailRenderer.material = lastCollidedBumper.material;
}

I discarded a few things for clarity.

Now, here is the shortened script for the split ball power-up:

void OnTriggerEnter2D(Collider2D collision)
    {
        if (!CollidedWithABall(collision))
            return;

        Ball mainBall = collision.gameObject.GetComponent<Ball>();

        // I added this part as a desperate attempt, didn't work.
        mainBall.trailRenderer.material = mainBall.lastCollidedBumper.material;
        Ball splitBall = Instantiate(mainBall, pos, Quaternion.identity);
        splitBall.tag = "Split Ball";
        splitBall.GetComponent<TrailRenderer>().material = mainBall.lastCollidedBumper.material;

        Destroy(gameObject);
    }

    private bool CollidedWithABall(Collider2D collision)
    {
        return collision.gameObject.CompareTag("Ball") || collision.gameObject.CompareTag("Split Ball");
    }

pos is a Vector3 variable that is declared in the cut portion. After getting the power-up, this is how the game scene looks like:

None of the balls touched a bumper after getting the power-up. I expect the split ball to have a red trail but it doesn't. I'm sure I'm missing something with Instantiate() but I don't know what.

One thing I assumed was that Instantiate() used the prefab of the main ball, in which case the trail would have a neutral color, but I added an assignment statement after Instantiate() so I don't think that's the only problem here. For reference, the split ball DOES change its trail color when it hits a bumper.

Thank you and please let me know if you need additional information.