Because MBs during that era were basically Chryslers. MB picked up on the cost cutting when they owned Chrysler and produced a lot of junk during that time.In later years they got back to producing quality products.
Now it is true Mercedes suffered through a lot of QC problems during that era. But I've studied this and evidence points primarily to maintenance issues. Around that time, powertrains were refined, many models shedding superchargers for naturally aspirated engines, a move to pure synthetic oil was made in the more mass-market models, and to compete with TCO numbers from BMW and Audi, Mercedes set 15k mile oil change intervals. They pulled them back in 07/08, released the stunningly reliable W204 C-Class, and things have been on the mend.