It is understandable that those who opposed reconstruction might object to broader repairs on the city, since the argument about building a fortified city would be more compelling than building the temple. Reconstruction on parts of the city other than the temple also happened during the period prior to Darius' reign (compare Haggai 1:3, 9) so it's not as though only the city or the temple has any reconstruction done at any particular time.
And yet the walls and gates were still a shambles in Art's 20th year. Sure, there was other building going on before Darius but it looks as if it was centered on people's own homes and comforts.
So I still don't see good reason to assume that the chapter does not present events in chronological order. The plain reading of Ezra 4:21-24 is fairly straightforward that an order was sent to halt work, then people forced the Jews to stop work, and then work was halted until Darius' second year.
Well, we'll have to agree to disagree. To me, the plain reading is that Ahasuerus/Xerxes and Artaxerxes were meant and that Ezra (or later redactor of Ezra-Nehemiah) wanted to summarize all the opposition to both temple- and city-building, from Cyrus, through Darius through to Artaxerxes in that one slot.
If it were actually Artaxerxes I who caused construction work to be halted, it would be spectacularly poor writing to leave out such significant events out of the the narratives in Ezra chapters 7 & 8 and in Nehemiah.
Why mention it again? It was already mentioned in ch. 4 and that was all the information the writer/redactor was able to or chose to share. As the letter was undated, rather than omit it or place it somewhere else which could have been equally out of chronological sequence, he decided to include it in the 'history of opposition' section.
Of course, none of this has any bearing on the JW dogma. I like to think of it as the adults talking while the JW apologists play in the sandbox.
LOL.