I think much of his strength lies in skills that other people don't hold high regard of. Like he told the robot dude, he cares a lot about his empire, remembers all the vassals that have passed. He's a sympathetic character and he's determined to do his best (stayed up studying to make sure the deal would be fair and that they wouldn't fall for their tricks). Those aren't weak traits, but we hardly ever recognize them in leaders or require them of leaders because it takes "too much energy." But that's how he leads them too. He knows each person's strengths and weaknesses and he delegates tasks to them accordingly. His confidence is at rock bottom because he knows he, himself, is weak and he knows how vulnerable he is without his people, because his Grand Duke reminds him of this constantly, but instead of recognizing that he has a community that wants to be his shield he constantly blames himself for not being stronger.
And I think that's the point. Showing us that strength is more than what we perceive it to be. It's our kind of mindset that keeps our MC weak af and has other characters underestimating him.
But I don't like the current ship, and I am mad because wth everyone but MC is strong af, not only physically but emotionally too.. I had my hopes because it was game like, so I thought he would find ways to get stronger but here I am