A lot of older games were bigger because of static assets. Riven (myst 2) was fucking huge because it was like 60,000 jpgs. It was on 5 discs. Later games running in a 3D engine just had texture files and small models, they were a lot smaller.

There’s that quake 2 clone that team did a while back that was only 92KB- it generated everything in memory on the fly. Krieger I think it was called?