The WB complaint is much bigger then a single phone call, the core of the complaint is center of effort by not Trump himself so much but his personal Lawyer Rudy Giuliani and his effort to undermine the U.S State department to secure leverage against Joe Biden.
The crux of the WB complaint is more so with Rudy Giuliani working on behalf of the President either with or without direct knowledge to pressure the Ukrainian government into investigation Joe Biden and his son.
this effort started in 2018 when Giuliani met with acting head of the Ukrainian DOJ Yuriy Lutsenko in NY and Poland were he tried to pressure him to open an investigation into the Biden, Yuri refused and has come out publicly since stating there was no merit for any such investigation under Ukrainian laws.
The WB complaint also goes into how the Ukrainian government felt pressure because they were being dealt with on two separate official channel one via the State Department and one via Giuliani who both wanted separate things.
now where Trump comes into play is his refusal to authorize military aid to Ukraine after this breakdown in communication, there is no proof that this refusal is directly linked to Yuriy Lutsenko refusal to open a investigation but that is very much what Giuliani wanted based on his public attack on new President Volodymyr Zelensky claiming his government was full of enemies.
now we get to the core of Congress issue with the WB complaint the phone call in which Trump asked Volodymyr Zelensky to do a favor, that favor was to open a investigation into the Biden something his personal lawyer has been pushing for.
now I don’t think Trump is the mastermind here this complaint very much forces on Giuliani and his influence over the President, but the question is will Giuliani gambit bring down his Presidency.
Trump could easy defend this impeachment by distancing himself from Giulaini and suggest he had no knowledge of his gambit.