Conversation so far:
What was her sound?
generic and "undistinguished punk-inflected hard-rock.
Are there any other interesting aspects about this article?
Critic Simon Reynolds observed how the band's originality only "really became apparent as the songs got slower".

Question: why did she come to this conclusion?
Self-contained rewrite: Why did the critic Simon Reynolds come to the conclusion that originality of the band Joy Division "really became apparent as the songs got slower",