Just listened to the debate. Wow, Knechtle was a diasaster for Christianity. Basically fallacious arguments ad naseum. He would not engage in any honest discourse nor answer simple questions. I know Dillahunty really wanted to hang up on him!
How could you possibly engage in an honest debate while maintaining irrational Christian ideas unless you are incapable of also engaging in a rational debate?
Matt is paid for his engagements by the parties (or a mutual host) who are often seeking to make fools of atheists in front of their audiences. I suppose I've seen a few hosted by objective parties, although I question the sincerity of their objectivity. I'm not aware of any atheist debaters who aren't paid by a host or opponent, though it wouldn't surprise me to learn that some cultists do it purely for hubris reasons.
It's not really a matter of convincing anybody when it comes to these "debates." If anything, for Matt or the atheist on that side of the debate, it's about demonstrating to the other side's supporters that they are prepared, intelligent, practiced and rational.
I find it incredibly entertaining to watch the best atheist debaters back cultists into corners. Usually they don't lose any face to their audiences, but for those not under the spell it's an excellent reinforcement on some of the old classics. Every once in a while, you get to hear something particularly outlandish of the sort that as part of a conversation on any other subject would be immediately called out and ridiculed.