The article's author explains several facts which establish both strong motive and abundant opportunity for Russia to strike the Nord Stream pipeline. 

Simply on that basis alone (existence of strong motive and likelihood of success) Russia is the most likely suspect. Two factors that the article does not even explore are (1) Western nations do not have a history of using terrorism against adversaries. Russia does (including recent strikes in the course of the Ukraine conflict) (2) Western nations don't have a well-developed capability to execute such a strike successfully without detection - Russia does. 

Those are two fairly compelling factors in determining who might be at fault in the sabotage. A third is the risk/reward balance - if a nation like the U.S. were to be caught doing something like that, the down-side for them (us) would be nothing short of catastrophic in a diplomatic sense, especially for the Xiden regime. Imagine the consequences in international relations for the U.S. to be caught destroying an ally's pipeline. It's not an overstatement to say it would be severe. There is no comparable up-side to doing something like that to the pipeline for the U.S. since the system was already not operating and European sponsors for the project were already on the defensive diplomatically, having chosen to suspend all commerce with Russian suppliers already.

Admittedly there is a slight chance of ever securing material evidence of Russian culpability in the sabotage, which is indirectly another indicator of their likely involvement (they knew it was going to be difficult or impossible to determine the bad actors from forensic analysis of any material evidence).