Trial lawyers ruined GA, though the FAA helped. They found that juries would award ten times the compensation for a death in an airplane compared to the same person’s death in an automobile. Deep pockets law made manufacturers pay, even where the pilot was in error. Liability insurance went from low single digit thousands per aircraft to a hundred thousand, more than doubling the cost of the average aircraft. Demand tanked, further increasing unit costs as fixed cost were spread across fewer units.
20k annual unit production in the 60s became low hundreds annually in the 70s, with prices ten times the average worker salary instead of two. Every manufacturer either went bankrupt or sold out to a larger company, who then refocused production on the more expensive turbine aircraft. Lack of funds made FAA certification costs unmanageable, so nearly every piston aircraft you see now was made in the 60s.