While I also doubt Russia blew up the dam (because I don’t really see a good reason for Russia to do so), I imagine that if the russians were behind it, they would have blown it up instead of just opening it, in order to be able to plausibly deny their involvement in the flooding. There could also have been technical reasons for doing so (maybe opening it wouldn’t have allowed the required flow for whatever goal they would have had?).
While I also doubt Russia blew up the dam (because I don’t really see a good reason for Russia to do so), I imagine that if the russians were behind it, they would have blown it up instead of just opening it, in order to be able to plausibly deny their involvement in the flooding. There could also have been technical reasons for doing so (maybe opening it wouldn’t have allowed the required flow for whatever goal they would have had?).