Puts Trump in a bad spot if he doesn’t show; all the candidates and the three anti-Trump moderators will be taking free shots at him for two hours.
Part of me agrees with you.
It would be interesting to see if he and Cruz both teamed up to protest the moderators.
If he decided to not attend, he could stream his response on another venue. Lots of them out there.
Run it at the same time. It would probably get a larger viewership. Have ads and give the money to the Vets.