I had those. I am pretty sure they were huge because everything was mostly uncompressed.

I remember using a program to extract game data. Every environment was a literal bitmap image the size of the area, and there were additional bitmaps of the same size for each, where pixel colours were used by the engine to check where characters could walk, what part of the scenery is overhead, etc.

It was cool looking into the adaptive music though. Every track was split in multiple bits of like a dozen seconds, so for example if the battle theme needed to end it could branch into a specific ending variation seamlessly. I don’t think a lot of games did that back then.