This doesn't say much. Competition was Mario Odyssey in 2017. I would also add HZD to that but I think it was a much harder decision between the first two. I don't think RDR2 had that much of an impact on being groundbreaking (as goty pick) in the sense that it was different from the previous iteration like GoW4 was for the franchise and BotW vice versa.
Those giving the awards disagree because RDR2 has received a huge number of GOTY picks. It must be one of the highest second places ever along with GTA V which was beaten by TLOU.