For a long time they were wondering why the Trump campaign is not using it, or why the media was not commenting on it, since it was so obvious. Or even if DNC knew about it when they made him the candidate?

The same circles figured that during the debate Trump did not give Biden enough time to be incoherent and forget where he was, or for what office he was running for. Even if Trump's advisors told him to allow Biden room for gaffes, he just doesn't have it in him to stand back and not interrupt when his opponent is making a mistake.