If the GOP nominates a Christian nutcase, of course a Democrat can win.
So it is the "Christian Nutcase" factor that cause this loss? It wasn't the 38 year old lies and the deliberate back stabbing by Jeff Flake and Richard Shelby (among others) that did him in?
Why then did he win his Supreme Court seat with over a million votes? He was even more of a "Christian Nutcase" back then, wasn't he?
I think there is something fundamentally wrong with your "Christian Nutcase" Theory. It doesn't actually fit the available facts, but what it does do is conform to another theory I put forth in an earlier message.
"Everyone wishes to believe that Christian people are hypocrites"
Roy Moore lost because two liberal kooks made 38 year old unprovable accusations against him, and the national media weapon amplified these unprovable accusations massively, while the Republican party first cut his funding (alleging the accusations to be true) and then restored it (after the damage had been done) and then prominent members of the party urged everyone to support the Democrat. (Jeff Flake, Richard Shelby, Mitch McConnell)
So the loss is caused more by false accusations and backstabbing, and not so much by being a "Christian Nutcase." The people of Alabama were fine with a "Christian Nutcase" back in 2012.
It is the lying accusations and backstabbing that changed between 2012 and 2017.