While the Saintess plays her own part, her manipulation of the hero is only possible because he failed to find value in what his adopted family tried to teach him. That being said, it would also be the Miria Family's failure as well. They basically fostered all responsibility of a self entitled shit of a hero onto a child. One who had no hope of forcefully motivating a headstrong ignorant twit into learning life skills and abilities that would be useful as a noble and hero for the kingdom.
@feha
Nah, even if he skipped all his lessons, he is still responsible for his own actions. Granted there is something to be said about the adults in hjs life, I get the sneaky suspicion that the MC isn't the only isekai-ed character in the story. He acts too self aware and is utterly certain in his belief that MC's family is evil and will be destroyed.