Why do you call the hatch-back C class a "failure"?
When Mercedes released the W204 C-Class platform in 2008 it dropped coupe and hatchback options. It was a new platform and they chose to offer only the sedan at first. Of course in 2010 they introduced an SUV on that platform, then in 2012 they introduced a coupe. The W203 coupe wasn't a failure but it wasn't as high of priority as introducing the W204 sedan.
When Mercedes released the W204 C-Class platform in 2008 it dropped coupe and hatchback options. It was a new platform and they chose to offer only the sedan at first. Of course in 2010 they introduced an SUV on that platform, then in 2012 they introduced a coupe. The W203 coupe wasn't a failure but it wasn't as high of priority as introducing the W204 sedan.