PEST's reason for existing seems to be to push Hybrid out of K45. This seems to be the only goal, it is all they want to talk about. And indeed, through decent co-ordination and good team-play they have, over the weeks since their declaration, gained villages. The fact that every other tribe around them is growing far faster doesn't matter - "death to the barb-munchers" is the mantra they are happy to decline under. Every nuke hurts Hybrid, and that's what is important.
Hybrid, though populated by players of a more modest size, have not been so narrow minded. K45 is going to be very difficult to consolidate. When PEST are no more, there are still Bi and O.O to contend with. Hybrid may triumph there, or any one of the others may. That is, however, a long way off. The leadership is not stupid: instead of throwing every nuke at PEST, they have moved north: K35 has been tamed, K36 is well on the way. To the east there is plenty of opportunity in K46 to meet Urban away from the central areas. To the west K34 is now easily accessible.
Hybrid has lots of territory, and opportunities in every direction. PEST is squashed in to 1/5th of an over-populated farmless pit of a K, with nowhere to else to expand. But with their "Hybrid is all that matters" mentality, taking a few Hybrid villages a week is enough to constitute success.
My dad's bigger than your dad.