My undergraduate thesis dealt heavily with medieval chroniclers so I feel like I can lend some information to this. The first issue I would like to address is that not all chroniclers dealt with a religious sub meaning, though many did. Chroniclers were people who wrote histories with an underlying message. For example in Marchionne di coppo di stefani bounaouti's discussion of the Black death in his chronicle of florence he discussed a heavy social and economic message rather than a religious one.

To answer your specific questions. I do believe that they believed in what they were writing. A chronicler wrote history in a very opinionated manner, something that is very odd to modern historians. Therefore they were choosing to discuss what they were discussing. To answer your second point, I will not say that all used it as a way of presenting damnation and showing the loss of humility in past generations, but that certainly was a topic. Gabriele de Mussis' Historia de Morbo certainly proves that this was a topic that chroniclers dealt with. I will not answer the last point directly because I do not have enough knowledge regarding the subject to do so but I will pose some important points that shed some light. As far as I know the clergy generally wrote their chronicles in Latin, a language that the clergy knew very well, but the laymen generally did not. The more wealthy might understand the latin language but it was certainly not a language generally taught to secular sections of society. So it stands to reason that these works were generally meant to be read and interpreted by members of the church. I hope this was helpful