If this was a protest it would be clear who did it. The farmers' have no incentive to mess with infrastructure without being visible for their cause.

Protests draw attention to your cause. This doesn't draw attention to anything, it is straightforward sabotage. Neither is it in line with how typical protestors operated before.

You are jumping to the assumption that foreign agents wouldn't be exposed, but any willing idiot can be bought to conduct such activity. Recent research in Denmark showed that sabotage comes, most likely, from locals, persuaded by foreign actors.

So two things could be true at once. A local 'protestor', disengaged through some issue (whether climate, farming or anything else), persuaded to join some 'resistance' by anyone.

I don't expect this to be supported by local protesting groups, like FDF or XR, either. Way too risky, media-wise.

Why is it sad for you for people to assume that recurring events with the same source are a base assumption to be made?