[2021] Horde night was broken?

Horde night is scaled to your progress in the game, also known as Game Stage. Your first horde night will typically be pretty easy, almost always ending before midnight. It gets progressively harder throughout the game.

Gamestage is a function of Player Level, and days since last death.

Basically, because of your chosen method of coping of taking an existing building and fortifying it, you didn't really gain any levels; nor did you have many days alive since it was the first horde night..So you get a really weak horde to compensate.