No sledging of crew here, because it can happen to any one of us...something that our mate Aircraft hasn't grasped!
Professionals do make mistakes Aircraft.....and you could make one of those mistakes one day. I'm sure the crew has learnt from it, but until you know the full facts, ie, were the crew rushed by ATC, was it a faulty flap guage, the crew may have thought they had done the before takeoff checklist etc etc, be very carefull about "dobbing" people in.
Another thing Aircraft, with good CRM, aircraft and systems knowledge, and a professional attitude etc etc we go to work in the aim of minimising mistakes. And if they do occur, we report them and learn from it. If you are an up and coming professional pilot, you may want to adopt a more humble attitude, thats no personal attack on you, just a bit of advice.