Anyhow, it's not his Financial traits that give people problems, if it was, then leaders like Wang would be lots of trouble as well. But here is a hint, one has a shinyness to wonders, another doesn't. And therein lays part of the problem. And of course, spiritual (one of the most under-rated traits) has its advantages too.
SPI is great for us but it SUCKS in AI hands...they can't even begin to take advantage of that and I'm sure you know it.
Most of the AI performance does not lie in its traits, but rather in its strategy "flavor", preferred improvements, and willingness to trade.
Joao is a good example ----> he favors science 1st military 2nd and will expand to a decent size, somewhat offsetting his average unitprob. If he gets that land, he's every bit as fast of a techer as mansa, possibly faster...so much for financial. Favored improvements are farms and windmills.
Cathy is flavored culture and military, usually thriving on size alone (and the creative trait, which the AI actually DOES use somewhat).
I could go on, but there have been AI lists done over and over in terms of who does well generally. With a few exceptions (like runaway shaka), the vast majority of the successful AIs have a middling peaceweight, are willing to trade tech freely (a far greater beaker multiplier than any infra choice or tile improvement), and are leaders that expand fast enough (or war successfully enough) to get a fairly large empire with which to apply the stupid AI bonuses.
As far as I can tell, the culture and science flavors take the AI down the lib path sooner than normal, too.
Good as mansa is as a techer, it's easy to see him putting up unimpressive #'s w/o some of his wonders. I actually fear somewhat more deceptive leaders like Peter, Bismark, Zara, and Gilgamesh more in typical games. All can declare at pleased, have unitprobs of 30 (only 5 behind monty), and tend to reach decent sizes (bismark is more of a wildcard, since he'll actually use nationhood and when the AI is in it, it will draft! Without that, he's not impressive though).
The only warmongers I respect are Shaka and Genghis Khan. Of the culture/wonder whores, I only care about them if they're a vassal to someone stronger or wind up feeding a powerhouse some tech. Rare is the game where they are the *real* reason someone loses, rather than someone else preventing the human from stopping them.