Higher education: Creative destruction
economist.com
economist.com
From the research I did it comparing MOOCs to other online education offerings this is merely one of the contributing factors. IMHO the primary factor to the failure of MOOCs is that they are massive. Recent research, highlighted in the NYT, showed that the introduction style courses - the ones with 300-400 students - suffer from the same or similar problems. Once they took some of the poorest performers out of the lecture halls and put them in classes of ~30 they outperformed the students in the large classes.
IMHO if course community were a large factor this high trafficked course with a high level of community discussion would most likely have exceeded this. As you say later ML courses have had much community discussion, yet they have had lower completion rates.
At the moment there is no substitute for real interaction with the docent or professor.