Major Turmoil! Ukrainian 20 km Strategic Bridgehead Wiped Out
Ukrainian officials claimed that Russian forces decided to blow up the dam because Ukrainians had gradually established control over all islands [in the Kherson region of the the Dnieper] and were ready to open a second southern front and conduct an amphibious operation. In fear they [the Russians] would not be able to cope with the Ukrainian offensive in Zaporizhzhia and Kherson simultaneously, Russians blew up the dam and wiped out all the Ukrainian positions on the islands.
[...] as a result the Ukrainian counter-offensive from the Kherson direction is temporarily canceled.
This short video also contains other useful information. He says the nuclear power plant should be safe because they can pump water up to the cooling pond. He also says the Russians planned a smaller release to just to flood the Ukrainians on the islands but (of course) the Russians screwed up and the breach got out of control. IMO this makes a lot of sense because a smaller breach and a smaller flood would not have cut off the water supply to Crimea.
I think this is the best and most coherent explanation to date. The Russians had a specific military objective: to stop the counter-offensive in Kherson. Unfortunately for them they cut off their own water supply and flooded their own region of Kherson by mistake.
I heard very little about this bridgehead after the April video I linked to previously. Many commentators downplayed it or denied it was a bridgehead. Then there was silence. At the risk of pretzel logic, this makes sense if Ukraine was trying to keep the operation under wraps while they slowly built up forces and supplies. Of course, after the flood, Ukrainian officials felt free to talk about the bridgehead and the planned Kherson counter-offensive.