A lot of people are wondering why MOOCs as a whole industry failed. I learned a lot from MOOCs, and can attribute much of my professional success to MOOCs. I can think of these reasons-
1. There are so much great content available for free, it almost doesn't make sense to pay for stuff.
2. Lots of universities, including MIT, NYU release their content for free along with handouts, assignments, problem sets, etc. And many great professors from other unis also release a lot of courses for free.
3. Much of the focus was on certificates, and honestly employers don't value them a lot, and higher education institutes don't value them at all.
4. Quality diminished in MOOCs. The early MOOCs from 2010s are of greater quality than the stuff that are released recently.
5. To make it in life, you are far better off with a university degree rather than without. And, people can't solely rely on online education.
6. MOOCs are expensive. Udacity nanodegrees were $1,000. My entire Master’s degree in CS was ~$1500 (in India).
7. They started focusing more on online degrees which almost no one value. And they are obscenely expensive. And platforms focus more and more on them. Think of Sedgewick's Algorithms course on Coursera. I don't see any new course of similar quality there. Focus is entirely on the online "degrees".
8. Good people left to do something cooler to them. The people who created Coursera, Udacity, etc. now do something else. Most provably some AI startup. People not similar to them are running the show now.
9. Coursera, edX, Udacity all have horrible, slow UIs. After a 2-8 minutes lecture (played in 1.5x) makes you wait a slow full 2 seconds to load the next page. And this is breaking, IMO. I would take a 2.5 hours university class lecture over this any day.
10. Unis use their own platform and abandoned joint ventures (?) because, maybe, lack of control. MIT has MITx, and some truly great new courses. I don't think they upload in edX anymore.
11. As per their behaviour, they focused on company-wide training, upskilling, etc. But I think most corporates don't look to upskill employees in a holistic way. They just want some tool specific training for their employees, that are too the point, practical in a negative way, and solely focuses on the tool at hand. Not every company is Texas Instruments, Facebool AIR, DeepMind, etc.
12. Despite all these, MOOCs are still successful, now often riding on particular people. They have their own websites with their own pricings, and own UI design. Think Jeremy Howard with fast.ai.
I think these are causes for the decline of MOOCA hype wave.