You can question a witnesses credibility but you cannot question hard documentary evidence, which each firsthand witness part of this investigation provide.
Witness Yuri Lutsenko, inheritor of Shokin’s office:
Records proving Amb Yovanovitch perjured herself at least twice.
Doc’s showing she was denying visas to witnesses who could prove Biden & Dem corruption.
Clear doc proof of money laundering by Burisma & Biden’s.