What matters for our outlook is not, in the first instance, whether humanity's failures in the past are attributable to malign motivations or technical incompetence, but whether the problem - whatever it is - is soluble.
If our major failures are ultimately the result of ill will, but humans are inherently malign creatures, or our collective endeavours are always undermined by the malignant actions of some individuals, then this would be little comfort indeed.
If people really believed that they wouldn't complain so much about it and they certainly wouldn't be politically active about it. There would be no point.
Arguably, this is true for most of the population. But there is a big loud minority that works very hard to make sure the correct lizard rules over us, so they must believe that not all humans are inherently evil.