How is this Doom Eternal still-picture-to-stretching motion video produced?
The overall steps are:
I. On a photo editor (Ps, Gimp, Photowhatever)

Duplicate the image several times, One per element of your final composition, for example. Background, player, monster 1, monster 2, ax.

Mask each element, normally with the lasso tool or similar, so you isolate the element on that layer.




For the background, you need to expand it a bit it to erase the element, You probably do not need to erase all the ax, just enough so when you move it you do not reveal the same ax behind the moving one.



Do the same on a monster if you need to delete some other monster part over it.

Export each layer as a single PNG file.


II. On a composition software
You could use Davinci Resolve, Hit Film or Blender which are great programs and free. Try with Davinci Resolve for this one.

Drag them into the timeline. Background on one layer, and monsters on another layer.



On the inspector Add keyframes on the scaling, making a loop.


For more specific information look for tutorials on how to mask, how to export and import files on the program you choose, and about the inspector on Davinci Resolve.
If you are paying Adobe, use Ps to mask and AE to composite. I prefer Davinci because you can see the waveform of the music, and playback in realtime to sync the animation.