Possible thing:
Long, long, long ago, Garenhuld made some sort of self-replicating (or even semi-self-replicating) robo-swarm. This swarm scoured the area of the galaxy around Garenhuld of life, but gained sapience, turned, and was about to consume the world entirely. Much of the planet's population died trying to survive, most all technology was lost, and the world's Guardian died burning all their might to erase the swarm, as well as burn the near-rabid need for TECHNOLOGY from Garenhuld's collective consciousness.
This resulted in a
Safehold-like rejection of invention and innovation, as well as a fear of the Unknown (perhaps a few tattered Swarm drones remained for a century or two out in the wildnerness before breaking down)?
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Another hypothesis:
Garenhuld's science once was enough to nearly reach the stars. But their advances drew the attention of something (*cough*
A DRAGON?!?!?!?*cough*). Thus their world is now isolated, and burned back to the dark ages.
Again, the Guardian burned themselves up defeating the foe, but the death-echoes of this final act, combined with the collective terror and mourning at what their innocent hubris wrought, scarred their collective mentality, and their souls, with a fear of the dark Unknown, and drove them far, far away from innovation and invention.
