It's no mystery if you consider the world at the time and the target audience.

Home computers were only a couple of years past where you had to solder the chips on yourself and still in nerdy kid domain.

There was a big overlap with the Dungeons and Dragans crowd. Puzzles and imagining yourself as some character were a huge appeal.

Now factor in that the underwear section of the Sears catalog was still the closest thing to porn as most 12 year olds could get their hands on.