Regarding MOOCs, part is that is likely cultural - some groups are more likely to have been enculturated in communities where independent learning and self-study is acceptable, if not actively encouraged, versus being discouraged by social ostracization or physical violence in others.
The broader issue of drastic differences in outcome, where some people can't get a job scrubbing toilets while others are getting 250k job offers, is also probably due to the winner-take-all employment environment that an increasingly developed economy creates. Use of technology amplifies productivity, so that differences between different quantiles of worker productivity become larger, and companies have more incentive to hold out for the potential employees at the top of the food chain. And as it becomes a more competitive environment, there's less incentive for the less competitive members to bother participating whatsoever. Since increasingly more of society's functions can be performed by smaller segments of the population it shouldn't even be that much of an issue, except that, especially in the US with its widespread "screw the non-contributing zeroes" and "let them die" attitudes, no one wants to consider restructuring the system to support the huge portion of the population that didn't "make it," despite that being the same population that the same highly productive individuals are being produced by and drawn from.
So my suggestion is it results from productivity differences due to technological advancement, and social welfare programs will not eliminate those differences, they can just help sustain the necessary population that will never be making 250k a year working as a senior engineer for a large tech company.