Whilst the evidence we have so far is circumstantial are we not jumping the gun a bit here?
There is always the possibility of pilot incapacitation or mechanical failure to consider, probably amongst others.
Interestingly enough I had a similar conversation with a PPL holder at the local airfield today at their cafe.
He related his story of getting off track one day in (for him) marginal weather and how if it hadn't been for a radar service he might have come to grief.
As an experienced (now almost retired) professional pilot (and instructor) in several different theatres of operation (but not helo) I then attempted to politely educate him that the pilots flying helos around London were highly professional aviators and that an inflight diversion in an area they are very familiar with (and the ATC services available) would be a "walk in the park".
Yes there is always potential for human error but I think it is far too early to damn the pilot before we know all the facts.