Putin’s and the Euro-Watermelon’s fault.
Probably they will blame Putin, albeit indirectly.
A lot of speculation on the proximate cause of this incident is being focused on government requirements to lower the ambient temperature in the lobby to a very low temperature, due to the energy sanctions, the temperature fluctuations and the relatively high temperature of the aquarium is thought to have setup some sort of stress cracking of the glass.
So yeah. Putin’s fault. Lots of lawyering up going on right now.