Definition: existing in a state of intellectual, moral, or social darkness
This seems to mean “be-nighted,” like “being in night” or “being in darkness.” Specifically, “night” seems to be intended as state of unknowing or ignorance.
If you describe people or the place where they live as benighted, you think they are unfortunate or do not know anything.
Why I Looked It Up
From an article in the NY Times about Kyle Rittenhouse:
There are those who believe that Mr. Rittenhouse’s actions were sensible or even laudable – the city had descended into lawlessness; the teenager, however benightedly, believed that he could offer some semblance of protection.
The point being made is that Rittenhouse was 17, and was ignorant of the larger implications of what he was doing. He was “in the dark” about all the ways his actions might play out.