It very often _is_ an anchor, and they are usually dropped and dragged on purpose for the effect of cutting the cables which are clearly marked on charts as places to not drop anchor
The chances of it being due to accident seems astronomically low, but I didn’t realize the intentional cutting was by an actual anchor. That makes sense though, as it would be an easy, discreet method.
I can't say I'm an expert on the matter, but my understanding from industry reporting on some likely intentional ones in the Baltic where that they were still unambiguously done with anchors. Just by someone intentionally causing the anchor to drop and drag along.
Cable cuts are very common worldwide and are very rarely reported widely in the media ( that I've seen ) unless there's an opportunity to tie it to Russia. Then it's reported as suspicious or there's a paragraph in the article speculating about the security implications of purposeful attacks on communications infrastructure. IMO it's a ploy to generate anxiety about how much money is being spent on "security" i.e. the military, and how we ( Europe ) need to increase it.