The article was behind a paywall so apologies if this is covered:
The dam sluices were Russian controlled but the dam is on the front line. It easily could have been attacked by either side. Both sides will see flooding but moreso the Russian side because it's flatter. Breaching the dam will empty the canal providing much-needed water to Crimea. The lower water level upstream could threaten the safety of an offline nuclear plant upriver. I can't tell which side controls the plant, so I'm not sure who that would affect more.
Russia could have easily done this to distract Ukraine ahead of it's counteroffensive and to make the river harder to cross. Also, Ukraine is likely more concerned about helping Ukrainians than Russia. But Ukraine could have done it for the reasons stated. We're definitely still in the fog of war and it's ignorant to assume we know all the details.