A First for me in Civ VI - AI Empire Wiped Out by City State

I've played over 1000 hours of Civilization 6 and I don't think I've ever seen this happen before.

I come across Pella (capital of Macedonia) with my scout while it is surrounded by Babylonian forces.

I plan to help Babylon just by providing zone of control in order to make it besieged. It ends up with just a couple of HP and my scout takes the capital. It rebels to free cities within 1 turn.

While I get the heck out of dodge, the Babylonian forces raze Alexander's other city. All I ended up contributing was one attack with a Scout.