It actually really helps that you've uploaded a webp version here. As you posted this, I was busy re-encoding this Ambient Swim video clip to webp to see if webp files work as both animated and non-animated images. I'll post it as soon as it's done.
I tried uploading the 5.7MB webm to Fedia, but it Mbin throws 500 Server Errors when I upload a webm of any type. I ended up uploading a 5.7MB bitcrushed gif, and linking to that 5.7MB webm on Catbox. I hope the Fediverse gets proper webm support soon.