Strange Facebook Ads Study Case - Comparison Inside!

Hi all, I'm advertising affiliate products via facebook ads and I'm doing some trial and error to get the best way to promote it. Today, i found strange facebook ads case....

So, I'm promoting fanspage post and created two ads for that post. These ads have same target market, which mean same age range target, gender target, interest, etc....all is same....The only difference I made was only on pricing, where one ad is using optimized CPM, and the another one is using manual CPM.

So, basically, it's all same, right? Same target market, and both of them are using CPM. Considering all of that, I would normally expect these two ads won't have not much difference in its performance.

But what i've got? This is the whole stat:



When these ads are same, why the stat is so different? The one that using optimized CPM perform very well (it's outstanding with 14% CTR...!!!!), while the another one that using manual bid (although it's way cheaper) perform very bad with only 0.036% CTR.

Yes, i know that the optimized one is already reaching 24000 target market, while the manual one is only reaching 6000 people. But if it's the case, why the manual bid's performances isn't even reaching even 1/4 of the optimized one? (because 6000 is 1/4 of 24000)

Any idea? I hope i can get enlightenment from you guys

Thank you