[vkou]

For the same reason that shooting down an Iranian passenger airliner or blowing up its centrifuges isn't considered an attack on Iran.

Also because most of us aren't interested in nuclear war over anything less than an existential threat. And the odds of conventional war between nuclear powers escalating into nuclear war is too fucking high. You'll need a better reason than 'someone blew up a weapons stockpile' to risk that.

If you're not going to risk open war over a full invasion of Ukraine, we sure won't risk it over an arms depot.

De-escalation-by-default is a feature, not a bug in a world where the push of a button can kill a billion people (much to the chagrin of people who have never had war waged against them).