They had to switch to David Sack's account to do the livestream and I think there were about 700k listeners that were on at the time of announcment. The issues weren't just infrastructure related, Musk had challenges with his mute button and it was creating feedback because he and Sacks were next to each other on their phones.
But yeah, it could have gone better for various reasons.
Are you sure ? Others say 6.5 M listened to the livestream that was delayed 20 mins