The exact reasons aren't entirely clear, originally they hated NS because it allowed Europe to ignore Ukraine in the gas trade which left them more exposed. By the time of the full scale war I would bet the reason was more "fuck Russia" than anything more carefully reasoned.
Why would you conclude this where every intelligence and law enforcement agency that has looked into it and published a report has found the opposite?
Do you have a basis to conclude that "every intelligence and law enforcement agency that has looked into it and published a report has found the opposite"? You exhaustively went through all Western intelligence and law enforcement agencies and read their reports? So you are quoting other news articles/interviews. Apparently their views differed. Ok.