This is a much more detailed look at the sinking of the Ursa Major, including how the vessel sunk and what it was doing at the time of the sinking.
An explosion in the engine room apparently, and she sunk stern first, indicating there was a lot of water coming into that area of the ship.
Never attribute to malice that which is adequately explained by stupidity. Or by incompetence. Or by neglect. Or by corruption. Or by vodka.
All those things existed before. Perhaps something changed in their ship maintaining routine to cut costs.
I’d like to highlight the Admiral Kuznetsov. Here’s my personal favorite from the wiki page