Except that this - invasion and conquest - was what the K'kree were already doing, when the manipulation was revealed to the top decision makers. Given how fanatic K'kree are, I'm sure that they were already pressing the conquest of Hiver space to the furthest extent feasible. So if the Hivers were able to have done this to several K'kree worlds while already engaged to such a degree, then what other horrors lay in store for if the Thousand Worlds if the K'kree persisted?

Consider: compared to the physical invasion which the K'kree were undertaking, a manipulation requires nothing tangible in the way of resources. To the K'kree, the manipulation would have seemed to be nothing short of an Evil Spell. How do you fight an Evil Spell, when you've never previously considered that Magic even existed?

Not that I think there was actually all that much rational decision making involved.  The K'kree leaders involved decided in a knee-jerk reaction to cover up the Evil Spell and then deny - even to themselves - that there ever had *been* an Evil Spell to cover up.