Hence the "insane", it means 2048x2048 base particles. That's over 25 million triangles (or 75 million vertices) per pass, and it's done twice (color and shadow mapping). Also the curl noise is pretty expensive, and 2048x2048 is quite a lot of operations. I think the browser locks before being able to allocate all necessary info, and if it does, probably the GPU can't keep up. Not everyone's card can push that much, but I've seen people getting to 4096!
