Possibility 1: Ukraine, which makes no secret of its desire to be admitted to NATO someday, launches a desperate, improbable and strategically counterproductive attack on the energy facilities of a key NATO member. Because, reasons...
Possibility 2: Ukraine, under genocidal attack and in an existential fight for survival, sees and exploits a target of opportunity in the form of a russian warship that strayed into their cross hairs. Russia, desperate to cover up the fact that its navy continues to take significant losses from a country with no navy of its own, obfuscates and comes up with outlandish and improbable theories as to what happened. In retaliation and in typical fashion, russia bombs a hospital.
I’ll go with #1, since Russia has been adding ships to the Black Sea since this military operation began.