What’s the big deal about Trump keeping classified documents at his house? He was the president, wasn’t he? He was the source of all power and legitimacy within the state, and everything in it was his property! Winning the election meant he owned the government, and could do whatever he wanted with it, just as he could with the Trump Organization.
Monarchs in the early Middle Ages did not recognize any distinctions between their private interests and the state; they were entitled to dispose of their kingdoms as they saw fit, subject only to judgment from God. There is no reason to believe that Trump sees the presidency any differently.