I can understand the pros and cons of the strategy.

Joe was more prone to making blunders when he speaks and when he has his guard down. He made a mistake when he said he does not support the green new deal. Trump interrupted a bit too much at times, giving Chris the justification to "move on" and let Joe off the hook.

However, at the same time, Joe spews outright lies left and right. The moderator and definitely not the media will not challenge his statements. So no choice, but for Trump to do it himself.