The "earliest, most basic cause" was not parking the departure helicopter on the correct location.
No, that is a strong contributory factor but the primary cause is that she landed too close (and with very good sight of) the other running helicopter.
If that square had been contaminated and was unusable due to a fuel or oil spill that the arriving pilot didn't know about and the aircraft had been positioned in the same way - but for a clearly good reason - then would you still blame 50% on the positioning crew? Of course not - it is down to the landing pilot to keep clear.
Whoknowsidont - sometimes operational urgency means getting things done as expeditiously as possible.