Reports from last year showed the presence of Russian spy ships in Nordic waters, the US has noted increased Russian activity by undersea cables in recent weeks, while only days ago a Russian vessel had to be removed from Irish waters. With tension between Russia and Europe at a historic high, it does not take much to assume this was Putin's doing.
There's a 1% chance that an investigation conducted by or on behalf of any NATO government will report that the US was involved in the destruction of the Nord Stream pipeline before 2025, according to the Metaculus prediction community.