Agreed, as a one-and-done. But it isn't uncommon for freshmen to ascend into more prominent roles, and then to justify a first round selection.
Malichi Richardson would be [if he returned] the team's leading returning scorer, the teams leading returning minutes played guy, and arguably the team's best shooter. He would be stepping into a more prominent role for a team that lost both backcourt starters--who were both double digit scorers--and would be looking for someone to both step up into that leadership role and be the alpha dog on offense.
There is nothing about Mali's play last year that suggests that he would "easily fall" under those circumstances, barring injury. To the contrary, all of the conditions would be optimized for him to excel this upcoming year.