Your displacement 3D model is stretching mainly due to incorrect UV mapping (uneven unwrapping) or misconfigured displacement texture settings (wrong scale/tiling).
UV mapping links the 2D displacement texture to your 3D model. If UVs are distorted, overlapping, or poorly unwrapped, the texture’s details stretch the model unevenly—this is the top cause.
Texture settings like too large a scale or mismatched tiling can also make the displacement effect pull parts of the model out of shape.
To fix it, use your software’s UV editing tools (e.g., Blender’s UV Unwrap) to correct UV distortions first. Then adjust the displacement texture’s scale/tiling to align with your model.