They are just too focused on short term opportunities without any similarities to a real player's planning.
My game today:
Being Japan, sandwiched between Russia and Aztec. While I have only a few musketeer and crossbows and a large GDT.
Seeing my lack of units, Peter decided to rush a wave of archers into my lands, joining with Monte's eagle warriors. And I crushed the invading units without much efford.
At this point, Cleopatra, with her leader agenda, denounced the weak Russia. And finally decided to march her chariots towards St Petersburg.
Yet, St Petersburg was walled and Peter withdrew all his archers, managed to hold the line.
Now with Cleo's pretty chariots all in the russian lands, her neighbors Victoria and Trajan decided it was the time to end her for good.
And then the peacful Gandhi further denounced their bloodiness and tried to end their violent rule with his elephants.
Then Gandhi's neighbor Catherine de Medici: Hahah, non siate sorpresso....
And Catheirne's neighbor Tomyris:
Trust is earned, do you not know that?
To my surprise, the WWI started in a sudden, at barely AD1450
These AIs.