You're in my lab. It doesn't matter if I did a lick of work!
Scientists didn't believe they had achieved all-knowing status...but the American public in particular was extremely impressed with how much mankind knew, and how much of it was because of the United States. This was accompanied by the science replacing religion arguments, and the prosperity of the country had people thinking the US was omnipotent and omniscient. This was the backdrop for the cosmicism that Lovecraft turned up to 11...I think it wonderfully fitting that even now we refer to his writing as the C'thulhu Mythos when C'thulhu itself was a pawn of true powers, a lieutenant at best.
- M