So for an accident to happen, a certain degree of lack of care - or negligence - is required.
I don't entirely agree, It is possible for a totally attentive and qualified pilot to just run out of skill enough to have an accident, though I agree that generally, for an accident to happen, someone missed something they should have seen coming, and that is, in some part, negligence.
In the case of Mr. Cox, and the ferris wheel, there are two interpretations of "did not notice" [the ferris wheel]. One is: Did not know it was there at all - that's negligent. Or, knew it was there, but lost situational awareness, and with the nose high, momentarily could not see it - error, not quite so negligent. As he reported doing a touch and go to check the runway, I hope that a view of any factors and encroachments to the operating area were a part of that check. So, having flown a runway check, and not ever noticing the ferris wheel, seems negligent to me...