I'm no programmer, so take what I say with a grain of salt.
However, with my limited experience fucking around with animation software, GIF files are WAY smaller than MOV files. I would assume that the dev re-rendered the animations from MOV files to GIFs.
If there is any content difference between the two versions, I couldn't say. But, if I'm correct, the older larger download would have better looking animations due to lower compression ratios during rendering.