A clip that performs well in one feed frequently underperforms when moved to another, and the reasons are partly technical and partly conventional.
Every transfer re-encodes the file
Video is compressed on upload, so a clip downloaded from one platform and uploaded to another has been compressed at least twice, each pass working from the damaged output of the last.
The damage concentrates in fine detail and in areas of rapid motion, which is why widely travelled clips look soft and blocky in ways the original never did.
Text suffers most, since compression handles hard edges poorly, and captions that were legible originally become difficult to read after two or three transfers.
Metadata does not survive the journey
Audio attribution, creation details and any link back to the source exist in the platform's own records rather than in the file, so all of it is lost when the video is downloaded.
The receiving platform sees an ordinary upload with no history, which means none of the discovery mechanisms that grouped the original with related material apply.
Visible watermarks are what remain, and some platforms actively demote material carrying another service's mark, which reduces distribution independently of quality.
Conventions differ between feeds
Each platform develops its own expectations about pacing, caption style and how directly a video addresses the viewer, and audiences read deviations as unfamiliarity.
A clip transplanted unchanged carries the conventions of its origin, which is often more noticeable to the receiving audience than anything about the content itself.
Aspect ratios and safe areas differ as well, so overlays positioned correctly on one service can be obscured by the interface on another.
The audience arrives with different intent
Feeds are entered in different states of mind, and material that suits an audience browsing without purpose may not suit one that arrived searching for something specific.
This is why the same clip can find an enthusiastic audience in one place and indifference in another without any technical difference at all.
Republishing properly avoids most of it
Uploading the original file separately to each platform avoids repeated compression entirely and allows framing, captions and length to be adjusted to local conventions.
The additional effort is small compared with producing the material, and it is the difference between a clip that travels and one that merely appears elsewhere.