There’s been a trend in recent years for the NBA Rookie of the Year to not just be the best player among their class but to also be a contributor to a playoff team.
Four of the last five players to win the award have been on playoff (or play-in) teams: LaMelo Ball last season, Ja Morant the year before, Ben Simmons in 2018 and Malcolm Brogdon in 2017. The lone exception was Luka Doncic for the 33-49 Mavericks in 2019, who was also maybe the best rookie of the last 10 years. That must be taken into account when looking at the betting field for Rookie of the Year.