To me, it means that they did not imagine, or see, a problem with economic differences between different groups in society, rather than actual conflict between those groups. Their reasoning for this is then given in the sentence which follows: "Economic growth would benefit everyone.......".
Use of the word "nor" with "did" makes it into the equivalent of the negative "did not" or "didn't". It is similar to the word "neither". It follows as an addition to a previous sentence or sentences.
"They couldn't drive through the flooded valley. Nor could they walk through the driving rain". (They couldn't walk through the driving rain. for which you could substitute "Neither could they walk through the driving rain").
"They weren't interested in singing. Nor did they want to play the piano".
Hopefully that will help.
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