That’s a fair question. Would a jury likely to be composed of at least some members of the LDS Church find that exculpatory to any degree or not? Would it even be legal to bring it up?
My intuition is that the prosecutor won't include much on LDS, perhaps a passing mention.
In the Indictment, each of the three charges for the murders of Tylee, JJ and Tammy includes the allegation that "Chad Daybell (and Lori Vallow Daybell) did endorse and espouse religious beliefs for the purpose of encouraging and/or justifying the homicide..." of each of them in turn.
So I think the prosecution will focus only on evidence that shows talk about the victims being light/dark, predicting the victim's future deaths, theories about the victims turning into zombies. Whatever is included in evidence, IMO, will shine the spotlight on how these religious theories were very specifically promoted as a way to persuade Alex to kill the victims.
This gets past their potential defence that Alex did the murders on his own, and also the question of his motive.
I notice Chad's name appears first and Lori's is in brackets. Perhaps that indicates they have evidence that the religious suggestions came primarily from Chad, and Lori picked them up from him and was persuaded by them, and in turn persuaded Alex.
That way he can't get away with the argument his lawyer wants to make, that this was a conspiracy between Lori and Alex, and Chad had no part in it.
ETA: but to go back to my point, in order to tie the religious beliefs directly to the murders, it's important to keep it simple and not get into a long rigamarole about tangential things like JR, or LDS prophets, End Times etc. The more focussed the information, the better it will persuade the jury.
JMO