The US were not thrilled about it when it was being constructed, obviously, but this was normal tensions towards Russia, prescient in the end but here we are.
There were several countries arguably interested in getting rid of that pipeline (Ukraine, Poland, the US), but Ukraine wanted it the most, had easy access, and there's no need to overcomplicate internet theories.
No, "normal" humans don't dive to 80m deep, where the explosion occurred. Any diver, whether professional or recreational (which is my case), will know about this. I don't have a (alternative) theory about this, I'm just stating facts. Well, the alternative theory, if we are speaking of divers, is that they had some very special equipment and were extremely skilled. It wasn't some random people, renting a random boat, renting random diving gear and buying random explosives ..
This simply isn't true, I myself after a technical advancement in my PADI to be certified on a rebreather went >80m many times. It's absolute more common than it was in the past.
Those who are trained with special forces as alleged would also be required to be qualified.
My main point is that it's not as rare as some might think, it's becoming more and more recreational.
The people who did it definitely took on risk, but in my eyes, more so because if something did happen to go wrong, there's no support to help you out (that we know of). It's a flying with 1 engine scenario. The fact that it was pulled off is impressive. But for any rec divers, don't try without the right training, equipment and people with you.