In lean, root cause analysis:

May involve applying the $5$ S$\text{'}$s applying the $5$ Whys

Takes too much time, so we have inventory instead and may involve applying the $5$S$\text{'}$s

Is often supported by cause and effect diagrams and takes too much time, so we have inventory instead

May involve applying the $5$ Whys and is often supported by cause and effect diagrams