It’s not just in movies. Think of ant and elephant
The strength of your muscles is based on how wide they are. Being longer doesn’t make them stronger.
As you get bigger, the cross-sectional area (width) of your muscle increases, but your weight increases more since you get longer too.
For example, if you become 2x bigger, that means 2x length, 2x width, and 2x height, and overall 8x heavier. However, your muscles, since length doesn’t matter, are only 4x stronger