He wants the votes. Then again, there are several people out there including the blogger whatifalthist and Ben Shapiro who don't claim to be Christians but advocate Christian positions because that ties more into an American ideal in the past they think we should bring back.
I think it is more that some people want ideals like:
1. Slow down of sleeping around outside of marriage and restoring marriage
2. Greater accountability for people making wrong decisions
3. To be fair, a lot of MAGA and Christianity is hostile to LGBT causes
4. Focus on a family-oriented cultural norm
Ironically, this has been common throughout history. We find writing after writing in Rome from pretty much every generation about how Rome lost its ideals and needs to return to a golden age of the past. Basically a Make Rome Great Again argument. Every civilization goes through this and there is some truth. Societies that are honest, family-oriented, more virtuous, more prudent, etc. tend to prosper while societies that are more materialistic, selfish, and sexually excessive tend to decline.
However, I am not sure if Trump is really about this or just about getting that vote. I think Trump somewhat believes, in his mindset, that America lost its way and in MAGA. The guy could make more money not being in politics but he seems all over the place and frankly, I don't see as much in common with MAGA fans and Trump on beliefs.
Trump and MAGA should NEVER have been a thing in the first place and frankly, to me, is a backlash (although an immature one) to current problems in our government and society. An early Southpark Episode about Mr. Garrison running for President as a representative of Trump hit it on the mark.
