They did this to try to take Trump off his game Tuesday night, that’s all. They know it will face, but they hope it will make Trump look bad on Tuesday night.
Trump just needs to stay the course, and focus on the task at hand, showing that Biden is weak. By the end of the week, this will fade along with everything else they tried to nail Trump with.
This is setting the table here. I could be wrong, but Trump is quite possibly the most strategic and calculating elected official in American history. If he were a military general, he'd be Napoleon.