“How America took out the Nord Stream pipeline”

Seymour doesn’t provide any proof or any evidence. It’s argument by assertion. What he writes is plausible but without any sources or other corroborating evidence. I think it more believable that Seymour has been paid to write this by a Russian aligned entity.

I don’t know the truth of the matter and Seymour could be right. We just can’t tell from the evidence provided.

The story is credible. Is it true? This is not enough information to decide that, because, as you say it, there are no sources or other corroborating evidence.

But it does host a starting point for future discussion due to the fact that it offers relatively detailed pieces of information.

Now it's up to others to come out and say "this is true, that is not", people who actually do have provable information. It offers them a story to share their information on. This story didn't exist previously in the public discourse.