What does this quote mean? I orginally thought that it meant that details are important, but when I searched on Google it looked like it means that God exists because of the details…
Well, since another saying is that the Devil is in the details, I’m not sure just how to interpret it. 
I’ve always taken it to mean something like this: if you think of a growing oak tree (say), you have the trunk grow up a bit and then split in two, and then grow a bit and split off another branch, etc. Science can tell us about the growing process and how the cells split and so forth. However, when you ask the question, why is every tree different? why don’t they all look the same, if the growth process is the same? … then you get the details are a mark of God.
Well, that, or chaos theory.
I had always heard it as “The Devil is in the details” as well.
Wanna build a car? No problem…just need an engine, some wheels, a frame to put it on and you’re good to go! Well…the reality is MUCH more complex and difficult…hence the devil is in the details. It’s the numerous little fiddly bits that will bust your chops every time.
“God is in the details” is attributed to the architect, Mies van der Rohe. It is a statement that while grand designs are, of course, wonderful, in the execution of those designs, it is in the careful rendering and faithful execution of the details that the Godlike process of creation is manifested.
Many people can imagine or sketch some sweeping overview of a dream, but if no attention is paid to the details of organization, construction, material, and the myriad other details that go into the actual creation, then the project will be nothing more than a shoddy facade that does not honor the original concept.
“The devil is in the details” was the corruption of that thought first widely broadcast by H. Ross Perot.
'nuff said.
Evidently “God is in the details” is a quote from the architect Ludwig Mies van der Rohe, who built the first steel and glass skyscraper. I did a quick Google search and found a bunch of sites that seem to back this up, but I also found attribution to art historian Aby Warburg and Flaubert. Personally, I first heard this quote in a book about Michelangelo.