Hmm, what's the speculation? Just that the low aura from previous Dreadgod visits causes it? Or related to the Sacred Valley suppression field? I don't see how the Dreadgod visiting is related.
My theory is that for reasons likely related to the mysterious Void Key owner we found, there's been a Dreadgod physically underneath the Silent Hinterlands for a very long time, which has caused the land's weirdness as a side effect - something that's such a subtle and widespread part of the area's 'background radiation', that Etaja has no frame of reference for it being unusual for Cradle rather than just being one more Foreign Iteration Thing he needed to get used to. Maybe he simply never had reason to look downwards hard enough to see the main body; maybe it's one of those things that are hidden well enough that not even
he can see it from a distance without expending enough power that it'd broadcast his own location.
Maybe the Dreadgod is imprisoned, sealed in a way that incorporates both the abundant halfsilver's unusual properties and drains the Remnants around the prison as a source of fuel- but now it's finally breaking down, potentially stuck in a downward spiral where the seal is starting to break down, so the drain isn't working as effectively, so it's got power supply issues that are breaking it down even faster as it tries to compensate.
Maybe the Dreadgod is recovering, having been defeated and seemingly killed ages ago, but not thoroughly enough that it couldn't come back given enough time. It's been consuming Remnants in the area around it ever since, rebuilding its strength bit by bit and potentially producing halfsilver as a consequence, but now it's getting close to reaching some critical threshold / got prodded closer to awareness / etc and so the consumption has slowed.
Whatever the case, if there is one here it's almost certain that Etaja himself was unintentionally the cause of things starting to change when he crashed face-first into this particular location years ago - we know from the very first update that if he hadn't come, Keras would've had a long, boring, happy life in this land until they died of old age, and the Dreadgod's arrival has been hidden from fate in the same way that the results of
all of Etaja's direct actions are (as we know from very personal experience); when normally Oracles would have been warned about something that affects Fate as much as a Dreadgod does literally decades in advance.