The reluctance seems, to me, to have a very obvious reason.
If we say that a) it was Russia, and b) that it was deliberate, we implicitly say there should be consequences for this event, and consequences for any further event.
We, the west, are simply not prepared to lay ourselves open to being hostages to such fortune. This is a 'Red Lines' thing - it's very obvious that there are NATO/US red lines, that Putin understands, and steers well clear of - regarding things like incursions into NATO territory, and use of CBRN in Ukraine, but I'm not clear that a concessusis presently there about the threatened (and deliverable) consequences of things like blowing up dams.
I would say it's a work in progress - and that just as the 'rules' of a year ago are not the rules of today, the rules of today are not necessarily going to be the rules in two months or whatever.
There a dicotomy: the weaker Russia becomes and is shown to be, the more it's Red Lines, and threats can be ignored - OTOH, the more it's threats and red lines are ignored and trampled on, the more panicked it becomes, and more likely to lash out to show how powerful/formidable/whatever it is.