At the reading of the accident report, I am surprised to see that the sudden loss of the left horizontal stabilizer resulted in such a violent pitch down.
The horizontal stabiliser is designed to produce a downforce in flight - helps keep the fuselage level. The two halves are often set at different pitch angles to generate a roll force to counteract the imbalance from a low-set tail rotor.
So, one side breaks off. Suddenly you have lost 20 or 30kg from 10' or 15' behind the cg - pitch down happens.
You lose the downforce from that side - pitch down happens.
You lose some of the roll balancing force - roll happens.
Add these together, 5h1t happens. Why did the owner succumb to the pressure to keep going without looking at the damage? It is pretty common for a wheeled helo to sink into soft ground and dislodge the brake hose lines.