Yeah, there's a lot of objects being rendered on screen. My GPU (3090 Ti) was running at about 41% while I was playing with the site. Amazing site, but definitely GPU intensive.
That your powerful GPU was putting in some effort while my poky GPU [edit: and my 2018 low-end Android phone, admittedly at ~4FPS] are still able to render the scene at all indicates to me that they put in some impressive effort to make the graphics scale for different configurations!