The engine did not reach full power on take off and the engine shutdown on the downwind leg resulting in a stall...

Yup. You can see the flame-out: the vapour trail stops. Take-off seemed OK though

Key mistake was that pilot did not full power test the engine before take off. I don't do that often when I fly my jets but I will now, at least at start of each session. The final turn wasn't a good idea either as it resulted in a stall. Hindsight is a great thing. You never stop learning in this hobby.