Strong Indycar ratings in the US, despite being up against the Masters: 1.055 million viewers on NBC; about twice as many as F1 which was a verrrry early start (568,000 viewers on ESPN2), but a little more than half of what NASCAR got (1.9 million).
One of the most watched non-Indy 500 races again, just like St. Pete was, although year-over-year comparisons are hard to come by because amazingly, this was the first Long Beach GP to be on network television since 2007(!) I guess it's true... back in the day, ABC would air the St Pete race in March and then completely and utterly forget Indycar existed until May...
And as for in-person attendance, the LB promoter estimated that the attendance beat the previous pre-Covid number, which was 187,000 for the 2019 running.
I'm not too familiar with american tv, when you say NBC - do you mean on their main national tv network or a NBC Cable channel?