From a tactical perspective, I think Kamala let this dance with Rogan corner her into a bad position. If she doesn't go on, she looks weak. If she does go on, she now looks desperate.
Her campaign should have determined earlier that she was going to do the show or not do the show. Then she should have just stuck with that decision.
Trump went on specifically to target young men who consider themselves independents and 3rd party voters. In the mean time he has gotten the endorsement of RFK Jr and now Tulsi Gabbard has officially joined the GOP. I think Trump is lining her up for big Cabinet Position. She is quite popular there.
Trump mentioned going after food chain additives. With an RFK endorsement (he alluded to him in cabinet) that will play very well with many independents as well.
The free speech tact is also in play.
So he, imo couldn't lose this one.
Kamala has no one to appeal to in Joe's audience. With no platform or policy to espouse to attract any if them. It would literally be a waste of her time. But in not doing it it continues to cement her image as a controlled puppet. It's a no win.
Does it move the needle? I think it does. By a few million votes. Will it be enough? Depends on where those votes land. He really only needs them in Penn State and Michigan.