Thermal Bloom
Humanity was the strongest race on earth. If not for the existence of Rhachis Ancestor Parasite, humanity would have dominated the earth eventually. It was a truth every Frenzy Beast with sufficient intelligence knew.
As Developers, they were especially clear about this fact. After all, every time they confronted humans, their numbers had to be at least thrice the opponents. And even then, they had a considerable chance of being wiped out.
That was the might of humanity, the strongest race.
Therefore, the moment they were being swarmed by the humans, the Lava Turtles first decided to defend themselves to the limit and seek reinforcements from the other three Frenzy Beast races—Floating Spiders, Spindle Bees, River Whales.
Only when combined would they be able to resist the might of humans and push them back. So from the start, they had been on the defensive. Even when their strength was evenly matched, the Lava Turtles didn't notice anything amiss.