He's telling the story, knowing exactly what sort of defence they would put up.
They complained about private testimony, so he made it public in a way that exposes the president's actions.
They tried the hearsay argument. He produced people who had heard the conversation between Trump and Sondland.
They tried the rogue actor argument. He showed Trump was instructing Sondland.
They argued Trump was interested in corruption generally, but Schiff had a witness who quoted Sondland as saying Trump didn't give a damn about Ukraine but only what helped Trump win the next election.
They tried disrupting the process. He smacked them down.
Trump tried tweet-bullying the ambassador. Schiff was watching and waiting for him to do so, readying an additional article of impeachment for witness tampering.
They twist and they turn. But Schiff is making them look very stupid and the president utterly guilty.