None of us know for sure anything about the drug allegations, although nothing would surprise me. However, I find it more surprising that China isn't more consistently competitive in the major athletic events. I was fortunate enough to visit one of the major Chinese sport universities a couple of years back, and the sheer number of athletes who were active in sport was staggering (and by 'active' I mean training seriously hard, not just 'participating'). The martial arts, boxing, and gymnastics facilities were literally full of students going at it 100% until they dropped, and the work the swimmers were doing was amazing. One of my guides told me she was the Chinese champion in her event and that she trained for two-three hours 13 times per week alongside being a full-time student.
The culture is also very different in that the students / athletes have great respect for authority and do exactly what the coaches ask of them. therefore its not difficult to imagine that an authoritarian coach such as Ma, given access to a large number of athletes, would find at least some able to survive a brutal training regime and consequently achieve amazing performances.
However, one thing I found very interesting in China was that the athletic tracks were the only facilities seemingly underused. Unlike everywhere else there were only a few athletes present who seemed to spend far more time stretching and jogging very slowly around the infield than actually doing any 'proper' training. I don't know where else they could have been doing any training because I imagine the life expectancy of anyone who braves the Beijing traffic to get a few miles in is pretty short!