Wikipedia doese assert that this vote is "[w]idely seen as a protest vote against the merger" citing a Russian-language article. A Canadian news site also reports that according to Acting Governor of Nenets Autonomous Okrug:

Yes, the majority of the inhabitants voted against [and] I am confident that these voices are not against the amendments [in the constitution], but it is a reaction to the issue of merging the NAO and Arkhangelsk Oblast.

I've not found any competing sources that substantially question this interpretation.

Wikipedia does assert that this vote is "[w]idely seen as a protest vote against the merger" citing a Russian-language article. A Canadian news site also reports that according to Acting Governor of Nenets Autonomous Okrug:

Yes, the majority of the inhabitants voted against [and] I am confident that these voices are not against the amendments [in the constitution], but it is a reaction to the issue of merging the NAO and Arkhangelsk Oblast.

I've not found any competing sources that substantially question this interpretation.