Yep you're right, I found just strange the fact of choosing the cardinal instead of his king, but apparently you think the opposite ^^Considering Richelieu was far more powerful than the king, I think choosing Louis XIII over the cardinal would be strange.
After thinking a little, having Richelieu as a leader is not a bad idea in fact, it's sad that they choosed CdM instead, she was not even French but Italian (as a Frenchy I'm a little offensed ^^)