Having trouble with a texture not showing on a generated mesh.

I am having a lot of trouble with perlin noise right now. This is the code I am using to generate the noise:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEditor.PackageManager.UI;
 using UnityEngine;
 
 public class NoiseTextureGenerator : MonoBehaviour
 {
     Texture2D noiseTexture;
     public Texture2D GenerateNoise(int pixelWidth, int pixelHeight, float xOrigin, float yOrigin, float scale)
     {
         Color[] colors = new Color[pixelWidth * pixelHeight];
         noiseTexture = new Texture2D(pixelWidth, pixelHeight);
         for (float x = 0.0f; x < noiseTexture.width; x++ )
         {
             for(float y = 0.0f; y < noiseTexture.height; y++)
             {
                 float xCoord = xOrigin + x / noiseTexture.width * scale;
                 float yCoord = yOrigin + y / noiseTexture.height * scale;
                 float sample = Mathf.PerlinNoise(xCoord, yCoord);
                 colors[Mathf.RoundToInt(y) * noiseTexture.width + Mathf.RoundToInt(x)] = new Color(sample, sample, sample);
             }
         }
         noiseTexture.SetPixels(colors);
         noiseTexture.Apply();
         return noiseTexture;
     }
 }

This is the script I am using the generate the mesh:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MeshGenerator : MonoBehaviour
 {
     Mesh mesh;
     Vector3[] vertices;
     int[] triangles;
 
     public Mesh GenerateMesh(int mapWidth, int mapHeight)
     {
         mesh = new Mesh();
         vertices = new Vector3[(mapHeight + 1) * (mapWidth + 1)];
         triangles = new int[6 * (mapHeight * mapWidth)];
         int index = 0;
         for (int x = 0; x <= mapHeight; x++)
         {
             for (int y = 0; y <= mapWidth; y++)
             {
                 vertices[index] = new Vector3(x, 0, y);
                 index += 1;
             }
         }
         int z = 0;
         int a = 0;
         for (int i = 0; i < triangles.Length; i += 6)
         {
             if (z == mapWidth)
             {
                 triangles[i] = a + 1;
                 triangles[i + 1] = a + 2;
                 triangles[i + 2] = a + mapWidth + 3;
                 triangles[i + 3] = a + 1;
                 triangles[i + 4] = a + mapWidth + 3;
                 triangles[i + 5] = a + mapWidth + 2;
                 z = 1;
                 a += 2;
             }
             else
             {
                 triangles[i] = a;
                 triangles[i + 1] = a + 1;
                 triangles[i + 2] = a + mapWidth + 2;
                 triangles[i + 3] = a;
                 triangles[i + 4] = a + mapWidth + 2;
                 triangles[i + 5] = a + mapWidth + 1;
                 z++;
                 a++;
             }
         }
         mesh.vertices = vertices;
         mesh.triangles = triangles;
         mesh.RecalculateNormals();
         return mesh;
     }
 }
 

   

Both of these scripts are called by this one:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class CreateMesh : MonoBehaviour
 {
     Texture2D texture2D;
     public int mapWidth;
     public int mapHeight;
     public int textureResX;
     public int textureResY;
     public Vector2 textureOrigins;
     public float textureScale;
     public Material material;
     void Start()
     {
         GameObject terrainMesh = new GameObject();
         terrainMesh.transform.position = new Vector3(0, 0, 0);
         terrainMesh.AddComponent<MeshRenderer>();
         terrainMesh.GetComponent<MeshRenderer>().sharedMaterial = material;
         terrainMesh.AddComponent<MeshFilter>();
         MeshFilter meshFilter = terrainMesh.GetComponent<MeshFilter>();
         MeshGenerator meshGenerator = FindObjectOfType<MeshGenerator>();
         Mesh mesh = meshGenerator.GenerateMesh(mapWidth, mapHeight);
         meshFilter.mesh = mesh;
         NoiseTextureGenerator noiseTextureGenerator = FindObjectOfType<NoiseTextureGenerator>();
         texture2D = noiseTextureGenerator.GenerateNoise(textureResX, textureResY, textureOrigins.x, textureOrigins.y, textureScale);
         terrainMesh.GetComponent<MeshRenderer>().sharedMaterial.mainTexture = texture2D;
     }
 }
 

For my material variable on the previous script, I am using a simple unlit texture. When I generate the mesh, it just appears grey, but if I open the material instance on the mesh renderer, the texture that it shows looks like perlin noise. So I guess my question is: Why isn't the texture being applied to the mesh when it is applied to the material instance?

If you look at the picture below, you'll see what I mean about the texture on the mesh not matching the texture on the material.