Well if this article insists this only happened because 21 savage is black, that's jut plain wrong. If that was the only reason, then it would have happened way earlier than it did. He came here when he was 12 and only had a 1 year visa and 21 savage definitely does not look 13 years old to me.
No this happened because some people don't know when to stfu. If he hadn't criticized ICE's policies he wouldn't have been investigated, and could have continued living in the USA and making rap. He's been a famous dude for a while now, and immigration services definitely had a file saying he wasn't supposed to be here. They almost certainly chose to ignore it until he decided to say some things he probably shouldn't have.
It would have happened if he was white or Asian or any other color as well.
It's like shouting FUCK THE POLICE in front of police while you're breaking the law. It doesn't matter who you are, you're going to get fucked for it.
The article does acknowledge this.... its up to you to read between the lines, the writer can emphasize whatever angle they like to make whatever point they like