How does light pollution interfere with the observation of low-contrast nebulas like the Orion Nebula?

It raises the background sky brightness, directly opposing the low surface brightness of the nebula and losing contrast.

Light pollution originates from artificial sources in cities and industrial areas, scattering light via dust and moisture in the atmosphere, which manifests as artificial skyglow. This phenomenon is detrimental to observing faint nebulae because it significantly increases the perceived brightness of the background sky. Since nebulae are characterized by very low surface brightness, they exist near the visual threshold against a dark sky. When the sky background is artificially brightened (e.g., to a pale grey), the already faint greyish nebula cannot be distinguished from it because the critical contrast needed for detection is effectively washed out or lost.