In their day these games actually had their art data stored as vectors, so could be even smaller than 4 bits per pixel! Plus audio would be midi, so just enough info for the computer to be able to roughly recreate the music. None of this ogg/MP3 stuff!
Oh yes I read about the original Kings Quest games, they did store the art as vectors, because they had to, it was the only way to fit it in RAM on the Apple computer. But Monkey Island etc. the ones your game looks like, they stored them as proper bitmaps.
Yes I completely skipped over mentioning the music :) Just plain note data...
@pixelartsierra has a bunch of gifs showing how the engine paints the backgrounds. Pretty amazing
https://twitter.com/PixelArtSierra/status/1622626172868722692?t=HOpy7xpGBbOzW0r6...