Every place where submarine cables are located is clearly marked on the appropriate nautical charts of the area, precisely so that ships will not anchor in the vicinity and damage the cables, not to mention ships losing expensive ground tackle. In most harbors or other holding grounds, there are usually extensive regulations and rules about where to anchor, for safety and traffic management reasons, and they are usually aggressively enforced by the local authorities. This has been the case for over a century, when overseas telegraphy first got its start. I'm sure accidents have happened in the past, but they have always been rare and, I'm sure, due to extreme incompetence or negligence. The recent flurry of cut cables may indeed yet have an innocent explanation, but I think it's still too early to rule out a sinister conspiracy.

Remember the old rule of thumb. Once: accident, Twice: coincidence, Thrice: enemy action.