Korah gathered the congregation, that they might be witnesses of the event, and, upon their success, which they doubted not of, might fall upon Moses and Aaron with popular rage, and destroy them. And it seems by this that the people were generally incensed against Moses, and inclined to Korah's side. The glory of the Lord appeared in the cloud, which then shone with greater brightness and majesty, as a token of God's approach and presence. See Exodus 16:7,10 Le 9:6,23 Num 20:6.
Related Commentaries of Numbers 16:19
Numbers 16:19
19 And Korah gathered all the congregation against them unto the door of the tabernacle of the congregation: and the glory of the LORD appeared unto all the congregation.