Yes, I believe he is just that dumb. I honestly think that Jamar likely sees the whole Flat Earth thing as another wave he can ride. Another "alternative" point of view that he can pimp. I liken it to how he releases a song like "The Elephant" at such an opportune time in order to capitalize on a hot button topic. For him, the very idea of being FBA is just another wave to jump on. In all honesty, he has been operating in this particular lane ever since he realized that inflammatory hot takes can keep his name out there via his appearances on Vlad TV.
In this particular case, Jamar's hustle got stopped cold and cut off at the pass by Professor Dave. Like Tariq Nasheed, Jamar's shtick only works so long as he stays well clear of anyone who actually knows what they are talking about and doesn't respond to the usual roasting and intimidation tactics. Jamar couldn't bully or clown his way out of an embarrassing situation and wound up asking the host to pull the plug. That's why you never see Tariq engage in real debates with actual intellectuals who aren't afraid of him or his penchant for roasting opponents. Jamar thought he was taking a bite out of a low hanging fruit and wound up nearly dying of food poisoning, but he's too arrogant to take the hint.