quicktime player created video combining separate audio and video tracks plays on apple devices but not in browsers

This 17 second clip I made by combining two files--the video track made by deleting audio track from original and then deleting video track from another copy of original and combining the two by dragging audio onto video--plays in photos and in quicktime player. But when I upload it, it reverts to the original combined audio-video track.

My programming skills are extremely limited but I was pleased to be able to produce this. I thought somebody more adept might find the problem interesting, like a doctor with a rare disease.