After some 10 games starting with various Game Options I have narrowed down where the AI fails in the start when playing Deity games.
You won't like this T-Brd, sorry, but it's Size Matters.
I don't like it either as I like that game option.
Probably some combo of that and the early spawn of strong aggressive animals nearby make the AI apprehensive to walk out with Str 1 units only to defend their Band with?
Minor Start, Raging Barb, Surround and Destroy, Fight or Flight, Hide and Seek, start with or without traits, Reckless Animals, Peace Among NPCs, Agg AI, are among those that don't make a difference, but as soon as Size Matters is engaged the AI stumbles in the start.
Tried with "Size Matters Uncut" too but same result, stumbling AI.
All done on Deity and going 70-80 turns into the game before checking if the AI had 2 cities or 1.
In ALL without Size Matters all AI had 2 cities at that time.
In the games with Size Matters all AI had only 1 city at that time, out of 6 AI's. One exception, in one game the Danes had managed to get a second city out.
So now you know where to look I hope T-Brd?
Cheers