christian theology doesn't apply well to the enneagram. that's why the holy ideas don't make sense. some Christians just love to run around seeing jesus in everything. also in my opinion, Christianity is a lot of bunk, but I was raised catholic, so I'll give it a shot.
So basically Holy Ideas are the things each type has to realize in order to "fix" their ego-fixation. The loss of these ideas causes the ego-fixations. So in order to fix a 1's resentment towards the imperfections of themselves and others, they have to realize that perfection is only achievable through god. In order for an 8 to stop seeking vengeance, they have to realize the "truth" that only god delivers justice, by either sending people to hell or heaven. In order for 6's to stop being "cowards" and "doubting", they have to have faith in god bc he will protect them and guide them. In order for 7's to stop worrying about planning, they have to realize that only god knows whats going to happen and trust him. And so on and so forth.
In my opinion, the holy ideas are completely meaningless unless you are a christian. If you are, I think they ultimately encourage inaction. We need people who pursue vengeance--dangerous people should not go unpunished in this life because they will be punished in the next. We need people who pursue perfection--we must hold our leaders to the highest standard possible. If perfection is achievable, improvements can always be made. We need people who act on their fears--we must be skeptical and alert. We need people who see possibilities and trust their own minds. The thing about the enneagram is that everyone's worst quality is also their best. Religion does not temper flaws, as history shows. (Not that atheism necessarily does either)