I'm listening to J.D.'s original video. He knows who they hired, has only met the dude twice, and is neutral to him (doesn't like or dislike him). What disgusts him is that the guy watched his IG stories of his dad and was probably trying to practice how to sound like him based on his grieving process. He knows the dude was on his profile since they don't follow each other. Also, the dude, the producers, etc. never reached out to his family for a blessing or anything like that like what was done with Paul Walker and Furious 7.
There's more, but basically the higher ups handled it in a messed up way. They (unofficially) offered him the role of the younger version. He suspects for a "feel good" story of his involvement; the role has been cast since January; so he's sure they're afraid about the backlash.