u/Boring_Treacle_7321

Hi can someone describe to me why this happened?

Turn 1: Ransacking city and nextdoor admin center, done in 1 turn each
Turn 2:
-City gets ransacked fine, Admin center gets ransacked
-but a new outpost is built right under my unit by black.(black was the previous owner)
-Then when my unit retreats they immediately upgrade it to a city :(

?????????
This game makes me so confused sometimes, how could an outpost be built under my unit?