The impeachment only needs the obstruction, which there is ample proof.
Trump asking for personal favors regarding historical events (that were debunked conspiracy theories) from another country to assist him politically, is sufficient to impeach, the holding back of aid is not necessarily needed for the impeachment.
Obstruction will be one of the articles of impeachment.
As for Biden, it is well known that Biden pressured Ukraine to remove the prosecutor, (he had wide ranging support to do so).
Noting:- Biden was pursuing US interests. Trump was pursuing Trump's interests at the expense of US interests.
