CPA Bid Stratgey on Google

Hi,

When we use a CPA bid strategy, does Google use our old conversions history only for showing up ads? Or they also consider other statistics also. Why I ask this question is I have moved a campaign to CPA bidding recently which got lots of conversions history. But when I checked the clicks generated on this campaign after moving to CPA bidding, non-converted keywords in the past is getting more clicks compared to the converted keywords. My question is if they were keen to get the CPA we targeted, they should have got us more clicks on converted keywords.

Thanks