During my early initial PPL training when I knew nothing; weight and balance was never routinely done. Two average men in a C152 with no luggage and maybe half tanks, is not often a performance limitation, I suppose - even on dry grass strips of adequate length. Whether my instructors did a perf calculation without sharing it with me, I don't know.
Having read the AAIB report, This pilot sounded either arrogant or stupid.
He frequently did not wear shoulder straps, and only did so when an instructor made it a condition of his instructing.
He did not seem to know or care about PPR, nor about limited grass strips.
He seemingly, did no pre take-off checks.
Having been told to back-track, he did not do so.
I suspect that on the fatal take-off, he struggled to get his speed up on the boggy grass, leading to a low airspeed and very marginal climb performance. And/or, he did not appreciate or compensate for the cross-wind from the right. This blew him left, heading straight towards the large stand of conifers, and he probably panicked. He either tried to pull the nose up to clear them, then realised it wouldn't work so tried to turn left away and got into a dive, or he stalled through over-pitching, and the left wing dropped.
Then towards the end of the AAIB report we learn about the cocaine in his body............
I don't know what to say, on several levels.