This is a fun, distinctive scenario, but the fixed score targets strike me as being an odd design choice (as well as being very high). If you're competing against a fixed target rather than the other civs, and if there's more than enough decent land to go around (maybe this shouldn't be the case...), it's not clear to me what the function of the AI players is supposed to be.
Might be because the AI is having some problems with the scenario.

This is from turn 41 and the settlers never settled.