BO4 probably isn't getting the hype because they basically just delivered a AAA version of PUBG. They didn't exactly bring an entirely new vision like GOW did, where as RDR2 looks to be more along those lines in terms of a much grandeur vision of the franchise.
I wonder how much the close launches of both games effected each other's sales though. Would either have made a billion if the other wasn't launching anytime soon? If BFV hadn't been such a screw up, would BO4 have done as well?