My theory... the first's equivalent of the Yok Huy were just... the Yok Huy.

At this point, I have the vibe that the Yok Huy and Ronka were basically on the same level if not several levels greater than even Allag with their incredible achievements, but the weakness of these giants is quite literally the same as the tripod aliens from War of the Worlds in that they have an unbelievably awful immune response to diseases and just die off en mass with one bad flu season.