I thought this back in the novel, and I still think this here: The whole "make mc a king, then suddenly avoid him like the plague, while conspiring to make his best ally a pariah to the state for some cheap shot at purging nobles I already know the name of" thing feels utterly stupid. With all that future knowledge he could have easily handled things differently enough to handle things adequately, and even if he makes mc king for his own conscience (what? why? mc clearly doesn't want to be king and he should have known that) he could have offered his utmost support from the get-go to have things end much differently and better. For starters, telling mc about everything from the start would have made a lot of sense.
MC needed to be king. The anime makes it clear that the Prime Minister doesn’t have the
authority to use the broadcast device. He would’ve had to go and get permission every single time. And, despite its massive knock-on effects, using the device is pretty minor compared to the really crazy shit he had to repeatedly pull, like hiring commoners or founding a new city.
If he’s got to go and get permission every time, not only does he get slowed down, but he’s limited to only trying the things he thinks can get approved. He won’t go truly out of the box, which is what was required.
And if the king is just a rubber stamp who only listens to his Prime Minister and always says yes, he’s no king at all. At that point you’ve ceded all authority to the MC anyway, might as well put him on the throne so he can get a PM of his own to rely on and use himself to make political marriages, both of which ended up being major factors in his success.
