What would Russia's interests be in putting these ISPs down, specifically?
I don't remember a single such case. I remember reading a lot of speculations like "it's highly likely that it was done by Russians" every single time without a trace of evidence.
It's undeniable that core European infrastructure is targeted currently
Personally I think the amount of special pleading required to imagine that it is _not_ Russia is a bit much (particularly around the deep sea cable cuts; at that point you’re really claiming that Russia is deniably pretending that it is them, but really it’s someone else), but you do you. It doesn’t change the overarching point; both Hetzner and OVH would be obvious targets for, ah, whoever it is.