because that is how the story was going until now.
the elder brother gave up his right of inheritance and expressed no will of reclaiming anything after his exile.
and the king himself never openly admit any wrongdoing to instead utterly crush the life of his older, his most loyal aide, going even so far to take his brother eyes, effectively condemning him to death.
just to uphold his power against even the smallest perceived bit of concern that it might be taken from him.
he even pushed for his son to marry the saintess, despite her brainwashing ability, just to gain more legitimacy.
royalty is historically obsessed to protect their position and since this is a japanese manga, japanese traditions of obedience and authoritarianism will be part of the narrative.
any kind of criticism and accountability against the holders of power will be suppressed.
Luke's actions against Will were the result of his mother's manipulations toward her own ambitions.
They happened prior to the present timeline, and were to showcase the folly of Luke as a ruler--despite what he thought was correct--and to both set up Will's storyline for himself and for his role in aiding Alicia's personal quest, as well as underpin the problems brewing under the surface of the capital when it comes to the actions of nobility and royalty.
Everything you're describing are plot-relevant actions that are clearly meant to showcase
exactly where Luke has screwed up as a ruler, and like
@lesseffective said, this chapter is quite literally the moment Luke-as-King is starting to question the actual reasons behind his actions taken in the past. None of this is the story itself seeking to insulate him from consequences; we're just not at the point where all of it's out in the open, for either Luke or any of the other relevant cast.
And your overall point about criticism & accountability would maybe carry more weight if we didn't have
all manner of manga, in this exact genre of isekai, that have kings and nobility and rulers be put in their place by "modern ideals" when the otherworlder shows up and tears them down.