The server hosting the file may be incorrectly labeling it as text/plain instead of a video format. This tells your browser to display the file's raw code as text rather than downloading it as a video.
If you are viewing the text in a browser window, try to "Save Page As" (Ctrl+S or Cmd+S) and change the "Save as type" to "All Files," then manually add .mp4 to the end of the filename. Download File dWmpbnf6wuZHlSrC.mp4
If one browser keeps showing text, try downloading the link in a different one (e.g., switching from Chrome to Firefox or Safari). The server hosting the file may be incorrectly