Why was the Dungeon of Dorukan so easy?

[Morquard]

His original purpose was to crack jokes about D&D players, and the silly rules of D&D, and to tell a story based on D&D with much irreverence.

Mission accomplished.

And one of those silly rules or tropes in D&D is that if a party of adventurers runs into a group of monsters, it's somehow a "level-appropriate encounter". Even if logically it makes little sense.