It seems like all the animations in this article are GIFs, not actual animated SVGs :(
I wonder why he chose to export them as GIFs after going through all the work to create SVGs. They also seem to be pretty choppy as a result. Maybe whatever CMS the article is using doesn't support SVGs?
https://happy-halloween.alfred-eichenseher.de/ (Halloween animation - click on the ghost button in the middle of the page)