The most important evidence is their state of mind as senior diplomats that U.S. POLICY had become that release of the aid was contingent on Ukraine announcing and conducting an investigation of a political rival of the prez. That’s not hearsay. It’s also bribery.
The second revelation was the overhearing of Orange directly discussing it over the phone. Will need the actual witnesses but the claim is that there are two.
Again, what would you be saying if these claims were being made against Obama?