Facebook has pixel size limits for images (that sometimes change) depending on where the image is displayed. Images larger than the maximum are either resized, or in your case treated as a scrollable view ("360 Photo" as Facebook calls it).

Theoretically there is a way to turn that off, if you click on the globe icon over the picture in Facebook there should be a paintbrush "edit" command. From the edit command there should be a toggle for "Display this as a 360 photo," but from my understanding this doesn't always work or that the command isn't always there.

I've also seen the suggestion that the file be saved without any EXIF data, so Facebook might not recognize it as a panorama. One way to do that would be to save it as a PNG file before uploading it to Facebook.

Note, if it did work, and then Facebook resized the image to fit whatever block it is in -- then the height of the image might be too small to see any details. Speculation on my part, but Facebook might favor the image being scrollable over the image being too small in one dimension. Unless I'm missing something, none of Facebook's layouts support arbitrarily sized images.