Plenty of people in Georgia, Arizona, Nevada, Pennsylvania, Michigan, Wisconsin, and North Carolina were paying attention to the event.
I'm just not convinced that DT Barnum's "base" isn't already excited. (Yeah, I know - double negative in that sentence) My feeling is that he needs to convince enough of those who didn't vote for him in 2020 to flip back. The grouping of voters who didn't really like Biden but were willing to vote for him because of the flipping "horse in a hospital" experience from 2016 to 2020.
I've read a lot about his base "capping out" at 40-42%. He needs another 6% to 9% of the electorate to gain the win.
The MSG event certainly didn't try to target the latter group; it targeted those who are already enthusiastic supporters. If you are pandering to those who already virulently support you, what does that say about voter turnout concerns?