I think you are right. Even though the answers are correct according to the question In my view thye answers should be B,F;H

First blank:
The sentence says: "That we may become flaccid after our rivals have been vanquished ... is in no way a(n) ______ observation."
"In no way" means "not at all." So it's saying this is not a ______ observation.

The next sentence says "Still, history is rife with examples..." meaning it's actually common. So the first blank should be something meaning "unoriginal" or "overly familiar" - because the author admits it's common, but says it's not a trite observation (even though it might seem so).

That fits B. trite.

Second blank:
"a sense of _______ pervades once a people have achieved victory."

The first sentence talked about becoming "flaccid" (slack, weak) after defeating rivals.
So the sense here is of relaxation, overconfidence, laziness - i.e., complacency.
That's F. complacency.


Third blank:
"Yet, even were this insight more _______ few would take notice..."

Meaning: even if this idea were more something, people would still ignore it.
If it were more "widely circulated" (G) or "clearly unassailable" (H) or "hastily dismissed" (I)?
"Clearly unassailable" = clearly irrefutable - even if it were obviously true, people would ignore it.
That fits best logically.
"Widely circulated" is possible but less strong - the point is about the strength of the insight, not its distribution.
"Hastily dismissed" doesn't fit grammatically ("were this insight more hastily dismissed" would mean it's dismissed more often, which doesn't match "few would take notice" - they already don't take notice).

So H. clearly unassailable is best.