As a general rule in a single vehicle accident, it's not usually the tree at fault.
Let's face it, aircraft are well designed, well maintained, and overregulated to an exhausting level, whilst all things are possible, we can probably rule out lightening strike, impact by meteor, in flight break up, bomb, pilot incapacitation, the ATSB will no doubt examine everything with a fine tooth comb, but this has all the hallmarks of a Garden variety EFATO not flown to a satisfactory standard, in an a/c that goes like a home sick angel on one engine, just saying.
It bears remembering, no one has managed to invent a new way to come to grief in and aircraft for the last 50 years, generally it is the same old mistakes that keep getting repeated.