He could have had poor training, maybe he wasn't even compliant with his Biannual Flight Review (BFR) who knows, but simply blaming poor training is not correct. One could have had perfect training, but became complacent or even totally negligent due to poor attitude, but that isn't poor training.
It seems he only purchased the plane ~7 months before the crash and in that time it looks like it was re-painted with other internal works done, so you may be correct in that he lacked adequate competency for the aircraft type. That is not poor training necessarily, as he may not have had a single lesson in the aircraft. That is poor attitude and decision making, not poor training.
Many pilots stall aircraft, for a variety of reasons, but poor training is very very rarely ever a causal factor. Stress is usually the most common fact and I would suggest this may also be the case in this accident. New aircraft, yawing to the left on take-off roll, stressed he pulled back too far on the stick and stalled.....On the internet 2 days later, it's an easy fix. Push the nose down and gather airspeed. In the reality of the moment, they guy made an obvious mistake and luckily he didn't pay the ultimate price.