Garthanos
Arcadian Knight
A solo adventure in an introductory set - especially a 'pick your path' type, which is what the one in Essentials has been reported to be - makes sense when targetting brand new players. It's a way to get some idea of what the point of the game is and how it might be played, even if you don't yet have anyone to play with.
Does it now? or did it then? as I said the sense that D&D was about team work was a really fuzzy thing barely expressed back in the day.