Why would they come back? Well if we wanna find that out we need to review some points and facts first…
After everything that these guys from the earth did in BW. It wasnt nothing more but a task force, a first wave… if not saying a scout wave.
#2.- Political interest
Yeah im saying it. We need to look at the UED just like we look at powerful modern governaments such as Russia or USA and China. (i dont wanna get politics involved pls) every country that want to invade or take more territory that it has already its because of a reason. ¿Why did the UED went to koprulu? Well… Powerful nations like to go to other contries if they have revolts or even revolutions. Koprulu in the BW time was a chaos and everyone was struggling for power or at least stability, none had at least a clear command chain or a fully established territory but the UED that had an entire part of the galaxy from themselves. like someone said they went to liberate the koprulu sector, to enslave the remainig protoss, steal their technology and to turn the zergs into their new generation zombie soldiers besides the UED said that the zerg was planing an invasion on the earth and that it was a inminent “threat to the earth” the perfect excuse to turn an entire alien race in slaves.
#3.- Lore evidence about their return
in the starcraft campaing when the UED expeditionary fleet (the scout wave) was erradicated by kerrigan she had a littel talk with stukov about the UED and their future return.
“They will come back someday, you know.”
“I do. And I will be ready for them.”
- Alexei Stukov and Sarah Kerrigan the UED’s future return
#4.- Compare Amon with Mankind (UED)
Amon tried to conquer and put the kopruluh sector on its knees and he used all his power and he was destroyed (yah yah yah i know that zeratul is dead thats sad).
The UED just tried to size control of Kopruluh in BW with a single scout force. The UED sized control over most of the zergs, They almost killed mensgk. Now imagine what would happen if they bring the full might of the UED to the next fight
#5.- We now that the UED isnt a utopia where everybody lives happy and free. in someway is somekind of overgrowth soviet union or somekind of ONU dictatorship and actually this gives an extra bonus in military capacity i guess we can all agree that dictatorship always brings a bit more military than democracy.
They will come back someday and you know it.