I have long known that this was an exceptionally poor question in its previous form. I've wanted to work on it, and I've hopefully got a good angle.
The premise refers to:
If one looks at nearly 360 major speeches that presidents from Franklin Roosevelt to George W. Bush have given, the increase in religiosity is astounding. The average president from FDR to Carter mentioned God in a minority of his speeches, doing so about 47% of the time. Reagan, in contrast, mentioned God in 96% of his speeches. George H. W. Bush did so 91% of the time, Clinton 93%, and the current Bush (through year six) was at 94%. Further, the total number of references to God in the average presidential speech since 1981 is 120% higher than the average speech from 1933-1980. References to broader religious terms, such as faith, pray, sacred, worship, crusade, and dozens of others increased by 60%.
—Coe & Domke, 'Think Religion Plays a Bigger Role in Politics Today? You're Right. Statistics Prove It.'
This sky-rocketing began with Reagan's use of "God bless America" to top off his acceptance speech in 1980. Did Reagan's use of "God bless America" in this speech reflect tones that were already present in the American political discussion on some level (local, etc...)? Did Reagan ever describe whether the effect of that decision—to top off his speech in that way which would greatly increase the use of religious symbology in presidential discussions—was to his liking?
This increased mention of the Christian religion and principles worked in Reagan's favour who tied the Christian evangelical vote with the Republican party—something that's been the case since then. Yet, the Politico article also describes how the evangelist vote has been of use in the congressional elections but not in the presidential ones:
On the presidential level, the Christian Right bloc has rarely been essential. Reagan’s two wins and Bush Sr.’s win were large enough that running up the score with evangelicals wasn’t necessary. Reagan had the economy working for him. Bush’s savaging of Dukakis rested more on his criminal justice record and national security positions than on his First Amendment views regarding “Under God” in the Pledge of Allegiance.
After that hat trick, the evangelical-dominated Republican coalition has failed to help deliver a majority popular vote in every presidential election save for 2004. Some coalition.
—Scher, 'When Reagan Dared to Say ‘God Bless America’'