What strikes me as the actual root cause is a lack of proper oversight.

Did any of these companies have a CTO who actually knows something? Did the founder hire all of his friends to work ((or ask them to help for free) ) with him regardless of their skills? Did anyone even identify what skills would be appropriate for building what was being built (having some sort of idea about the architecture would help here)?

Nobody knows everything. Don't have people working on things they have no clue about, or make sure you watch closely if you do.