Contradictory messages in a passage

Contradictory messages in a passage

The passage below is from Fathoms: The World in the Whale Hardcover by Rebecca Giggs.

I thought back to the whalefall, too: to the tiny creatures weaving a lurid carpet of decomposition over dead whales on the sea floor. Their lives were lived in a state of such impotent contingency, that, though I could imagine them as wild compared to parasites, I couldn’t think of those marrow-nourished annelids, isopods, clams, and sea snails as independent animals. ?They were more like fairy rings of toadstools that rose up after rain; ?possessed of a directionless persistence belonging to vegetables, or crystals encrusting a cave. ?They were an essence that flickered and ran.

In this passage the last two sentences seem to show contradictory messages.

Let me tell you what I mean.

#? talks about the tiny creatures’ essence of purposeless and transiency because fairy rigns comes about just after rain, but they disappear soon after that.

#? talks about the tiny creatures’ essence of aimless persistence.

#? again talks about their essence of transiency. (I regard ‘flickered and ran’ as ‘bloomed but soon disappeared’. Am I right?)

MY question is this, if my line of thought is right, then, isn’t it better that the author should put ‘But’ in front of #?. Am I right?

Thanks in advance.