In asking Zelensky to conduct an investigation that would benefit Trump personally, Giuliani and Trump behaved as if the government was at their personal disposal. They acted as if the U.S. is a mafia state.
Put simply: They conducted U.S. foreign policy for the personal benefit of Trump and pals. This is why the first Article of Impeachment is “abuse of power.” Yes, there were crimes involved. By the overall problem was behaving as if the U.S. is mafia state.