iKon fans are talking about boycotting iKon goods again to show YG that they're serious about the company actually caring for iKon.
From the screenshots of the video below you see him standing at the edge of the stage, taking a step forward, and falling into the open hole in the stage where the stage lift had gone down without him.
Stage accidents like this have been happening to Korean artists over and over again (much more than say, American artists) and people are criticizing stagehands in Korea and Japan for not putting enough time and care into the safety of other artists :(