Because most likely it's a work in progress gif from Hard-Degenerate subscribestar site and the X (formerly known as Twitter) user got it by subscribing or some other way and nothing more. Or else we would have heard about it by now if the full video was released.
Come on, just think for a moment, I know it's hard with all the blood not in the Head but damn some logical thinking isn't too much to ask.
dragon maid project dates from last year, guy really cannot manage projects, the latest one was shorter compared to the dragon maid one and it shows. Sidetrack but at the same time, he should have made it a bit shorter to maybe have another public release.