Simply put, lean production is fragile.
The evident supply chain fragility during C-19 speaks to how optimized our world has become. Quote is from here.
Mass production is simply lean production run by the rulebook, so that no one takes initiative and responsibility to continually improve the system.
The mass producer keeps the line moving at all costs but ends up doing massive amounts of rework at the end. While the lean producer spends more effort upfront correcting problems before they multiply and ends up with much less total effort and higher quality in the end.P117