but Riri had released only 2 singles from her last album that were successful and all ther other 3 flopped... Except if you're talking about Monster with Eminem...
Well then that's the case for every artist. We can always find someone who can perform vocally better than X, Dance better than Y and dress better than Z. Everyone is "replaceable" by your definition.
Trust me if labels had the choice between a Hollywood sweetheart who would cause them no problems and a PR nightmare they would go with the first option