Not just engineers
The team(s) "doing" the Airbus FBW system did not include "just engineers" but also pilots, some of whom also had high engineering qualifications.
Also, Airbus FBW wasn't a "one-off" programme, but the logical continuation of the control philosophies on preceding programmes, and many of the members of the FBW teams had been involved with those programmes.
Don't go along the "uncontrolled mad programmer/engineer" route - it doesn't wash !