mongol campaign. into china level. enemies not surrendering?

Hello new player here, playing aoe2 hd (from Steam) campaign mode. Mongol's "into china" level. Standard difficulty. The objective is to defeat the four chinese enemies and i'm having trouble doing that. Do I have to kill literally every single building, soldier and villager of each enemy? because i'm trying to do that but it seems one villager survives, runs off and the enemy rebuilds... and all of a sudden they have new armies with archers, melee soldiers, monks, siege weapons etc.. while I then have to rebuild my dying armies. Yet in some youtube videos i've seen of other people playing this campaign level the enemies surrender much easier/quicker. It seems like I'd have to put a soldier/guard tower in most areas of the map to completely shut one of them down.

is there a problem with my game?