To ensure they weren't going to be used anytime soon.
> Even if they think there is a 99% chance they'd not get caught, that is a 1% chance of completely destroying relations their with Germany, Scandinavia, the EU, and probably the entire world.
1. The US has a history of taking insane risks with clandestine submarine ops. Much worse risks than this; they did much that could have provoked the Soviet Union during the Cold War, when both sides were threatening each other with nukes.
2. If Germany/Scandinavia/EU/etc did find irrefutable proof that the US did it, they would probably bury that proof and pretend they never saw it. It isn't in their interest to break from NATO even if America did this and they know it.
We could fire missiles into many countries and they’d just take it for quite awhile at this time.
Germany cut itself off from Russian gas before securing an alternate source is pure Vasalage.
I think the much more likely explanation is that this was Russia or at least a faction within Russia. They are the actor that has already started a war in this area, has shown completely disregard for treaties and international law, and has been known to act irrationally (eg. by starting the war in the first place).