I was just thinking the same thing.. 300gb, mostly of presumably high-res art and video.. and that's 2 years work? Sounds really small.

2D Animation doesn't take up much space. Beyond a few painted high res background, most files are small and a lot of things are procedurally generated and take up almost no space at all. I worked on a 2D animated movie 10 years ago, and the data needed to render the final movie weighed in at less than 100 GB (and that was 2-3 years of work by 30-40 people). Also I understood from the story that they didn't loose everything, just enough to make it impossible to recreate the episodes without basically starting from scratch.

Two man-years maybe?