I can’t comment on this one specifically, but SVG animations take notably more CPU usage to render/animate in Chromium browsers compared to GIF or WAAPI. And they block the main thread for at least some animations.
That's pretty typical. Every element of an SVG is an object with a bunch of properties that can be manipulated and scripted and whatnot. It's great for a lot of things, but it's a lot more resource intensive than "dump this set of pixels onto the screen here" like GIF does or even "perform this set of drawing commands" like HTML canvas does.