I was playing Sid Meier's Civilization 6, was playing as China and decided to attack City State Kumasi. I took out it's walls with my catapult, pludged a farm and theiter district, then a few turns in (3 or 4?). I attacked it with a crouching tigger getting the city to half full hp. I ended my turn with out doing anything else except moving my warriors into place to cap. then during the cpus' turn, peace was made without me doing it. I tried reloading the last turn and peace came again. What is going on played a few other games and never had this happened, it seems noone else has experenced this. I would ignore it if it were Civ5 or something but now I have to wait 10 turns till I can attack again and it will piss off everyone to a point of no return I would think.
Why did peace happen and can I prevent it in future games, maybe even reverse it in this one?