Lets make this real simple. The impeachment clause of the Constitution describes three major assaults on the state as reasons for Congress to remove a president: treason, bribery, or other high crimes and misdemeanors.

In terms of Trumps interactions with Ukrainian President Volodymyr Zelensky, there is little need to engage in a debate over what constitutes high crimes and misdemeanors. Instead, they clearly fit the definition of bribery.

[B]ribery may mean the taking as well as the giving of a bribe, Charles Black, the late law professor, wrote in Impeachment: A Handbook, the definitive legal interpretation of impeachment for the past 45 years.

In this case, Trump appears to have used the power of his office to extort a foreign country (Ukraine) by twisting the good relations between the two and the military aid provided by the U.S. things the Ukrainian government is dependent upon into a bribe in exchange for a personal favor for Trump going into the 2020 election.

That the actions of Trump and his consigliere, former New York City mayor Rudy Giuliani, were an attempt to extort the Ukrainian government is clear from the whistleblower complaint and the summary of Trumps July 25 call with Zelensky.