A blob video?
Open the tweet in another page, open the browser console (typically F12 or ⌘ + ⇧ + i) and click on the Network tab. You will see all the resource fetched for the page, and among them there should be a m3u8 file. What is that? Simply a multimedia playlist!
Right click on the m3u8 file and select Copy URL. Now go to console and feed that url to youtube-dl.
It will fetch the playlist, download all the video segments and merge them with ffmpeg. It takes few seconds, and the result is the whole video, usually saved as mp4.