If I understand these things correctly, and I am not sure I do, isn’t the problem inherent in our government that the man and the office cannot be separate while the man is in office?

That is, in the US Republic, the President is both the chief executive and the head of state. The person as President. In a constitutional monarchy like the UK the head of the nation is the Queen, quite separate from the politician who is the head of the government. The latter is easily replaced, the former not so.

As the President, the person, is the head of state, to try him would be the same thing as trying the state, no?

Which is why the man has to be removed from the position of being the head of state, so he can be tried as himself, and not the state.

That, anyway, is how I justify the absurdity of the now-outdated US Constitution.