That was then. This is now and things are not the same. They want to win and they have tried almost everything to try and keep him off the campaign trail or prevent him from running at all.
The democrats don't even want Biden to win. If something bad happened during the debate, with these conditions, only the candidates would be hurt.
I don't usually think about things like this, but after what I've seen people do, I think something along those lines, is definitely not out of the equation for them.