I don't think "Rappers" have anything to do with Trump's increase Black turnout.
Trump was celebrated in rap music for the same reason America celebrated him in general. He was a symbol of success and capitalism and street rap is very capitalistic. So the man that embodied money here is going to get shoutouts in the music.
Anecdotally speaking, the minority idiots in my life that support Trump are bigoted, conservative about gender roles, and hyper religious.
Oh all facts.
I think people are saying Obama is assigning a 'cause & effect' attribution to rap, when he's actually doing a (admittedly very clumsy) correlation between the early 00's rappers who endorsed Trump, and Trump himself.
But also, at the same time, Obama is a near 60 year old Black man, who's out of touch with the current culture, and is pulling from values from a different generation. (But also also , you then have to consider how old are the Black men that voted for Trump, and are
they from that same era?)
tl;dr It's a really tough nut to crack without really granular data, which we don't really have yet. And that's why I feel like it should be kept between us in-house, before we get white people chiming in and muddying the water.
Sorry for rambling!