You read about the motivations of the elite in supporting religious institutions and dedicating their children to the regular and secular clergy, and you think, well, surely that's an arrangement of convenience or mutual advantage, mainly... but no, if you look at the data it really, really wasn't. They genuinely believed the whole eternal-damnation thing and took it super-seriously and contributed to the church in ways that were very much net-negative to them and their families (and that some others avoided doing to no clear disadvantage, so it doesn't seem to be a harm-avoidance measure, at least not in material or social terms). The norm, at least for a good stretch of centuries, was for these transactions to confer less in material or political benefits than they cost (though, sure, some were political power-plays or otherwise highly beneficial).
The thinking seems so alien that it's hard to really put myself in their shoes. Even the vast majority of the modern religious, and certainly the elite religious, at least in the US, don't act as if they truly believe like the barons and dukes of Europe did. The only place you see that kind of self-sacrificial dedication to religion these days is what we'd call cults.