Internal Sabotage?
Ukrainian strike?
Grease fire in the rooftop restaurant?
The Ukrainians have no interest in striking civilian targets inside Russia, so the attacks on Belgorod and Kursk far outside of Ukraine's artillery and drone range look like engineered provocations.
Putin may have decided to gamble on a larger escalation to try to finish off the Ukrainians by having Belarus attack the northern flank or start a general terror bombing campaign to increase pressure. Some of this may be driven by pushback Putin is getting from his own military who have felt constrained.
A broader conflict might drag NATO in, for example, it's hard for me to see how Poland will sit by and allow Belarus to invade Western Ukraine. For Putin either scenario may be a win-win: either he conquers most of Ukraine or NATO intervenes and he has an excuse to reach a negotiated settlement in a stronger position with Ukraine and a reason to rein in his military.
This would be the kind of unplanned escalation I have complained about as a possibility for a long time and would be another consequence of the incompetent cowardice of the regime in DC.
If it’s a Ukrainian strike, say goodbye to Kyev and Odessa.