That's surely more about convience, i.e. no one in Europe wants to actually deal with Russia so will faff around pretending they don't know who did it as long as possible
There's only three possible outcomes that have any chance of being true and none of them are good:
- It was the Russians, and the demands by the public to respond might escalate the current situation from a nice contained proxy war into something that might get actual voters killed.
- It was the Ukrainians, which would be politically awkward because we're supposed to be allies.
- It was the USA, which would also be politically awkward for the same reason.
So in all cases it would be better to not find out in the first place, hence the current faffing about.
Not sure it had to be a state operation. The attack could have been done by just a handful of guys with practically no funding. The pipe is not that deep underwater and would not require much incentive to blow.
It's the most monitored underwater area in the world and the magnitude of the explosion as detected by seismographic stations looked like a small nuke. Not sure a handful of guys would be capable of that.
