Populists (e.g. Trump) are not good at all in debates.
Depends what you think the point of the TV debate actually is. Trump, for all his flaws, instinctively understood the actual point of the televised debate, and crushed all his primary opponents. He knew that his target audience didn't care if he was right or wrong on any of the facts or detail, they want someone who looked strong and confident and commanding, so that's what he focused on.
The problem I have with modern-day debates (I mainly catch the political ones) is that they're not at all good or in good faith, there's a lot of "but YOU did this", a lot of dismissals, and no good structure; the moderator does not do their job very well in a lot of cases.
Mind you, that depends on the politician as well. Populists (e.g. Trump) are not good at all in debates.