I notice that their definition of "greater scientists" - which seems to have been what you referred to as "very successful scientists" - was "members of the National Academy of Sciences". While I have no doubt that one needs to be a pretty great scientist to become a member, the results lead me to wonder whether the membership process for joining the Academy has an atheist bias in it somewhere.
I notice that the figures for scientists generally are more constant from 1914 to 1996, with approximately 60% of scientists expressing "disbelief or doubt in the existence of God" - since the selection of respondents here is not subject to the (potentially biased) membership process of a single organisation, I would give this general figure far greater credence that it shows what it purports to show.
(Also, I think you may have linked the wrong page in your "scope for debate" link - it's linking to the same page as your "this summary" link)
whether the membership process for joining the Academy has an atheist bias
It's possible. (I suppose new members are nominated and elected by existing members, and people may tend to favour candidates who resemble themselves and be influenced by politics, religion, skin colour, etc., etc., etc.) It would need to be quite a strong bias to produce the reported results in the absence of a tendency for "greater scientists" to be less (conventionally) religious than scientists in general.
The last paragraph of the Larson-Witham letter to Nature looks...
Another month, another rationality quotes thread. The rules are: