The thing about Biden is he's been in Washington for 51 years, and knows how to work the system at "pinball wizard" levels. The man has a black belt in bureaucracy.
An obscure law lets the president give away $500M of military surplus a year... but he gets to set the clearance price of that surplus. Instead of giving stuff directly to Ukraine, he has other countries declare their old Russian weapons worthless "scrap" which he trades for US replacements.