My first reaction on seeing the title 'Is there explanation other than “Satanic ritual” for the Gotthard Base Tunnel Opening Ceremony?' was that the form of the question in the title is not suitable for Stack Exchange.
Yes, there are plenty of other explanations: Aliens. Drugs. Cultural gaps. Mass hypnosis. Illuminati. Parody. Prank. People not knowing art when they see it.
The question is, is it Satanic? But when I went to make that change, I found @ChrisW had just changed it in the opposite direction. I don't want to get in an edit war. Hence this note here.
We don't review art
Asking here what the underlying themes are for "The Great Gatbsy" is off-topic. Even if someone says F. Scott Fitzgerald includes satanic symbolism. It is a question of opinion and personal interpretation, not something that can be answered empirically.
It is the same for this performance art. Interpreting the themes and motivations of artists may be an interesting discussion, but it doesn't require scientific skepticism.
(Even quoting the artist about their motivations isn't going to answer these types of question.)
What is the claim?
I note that there is no extracted quotes of the claim. This is a concern because it means there is a risk of us tackling strawmen. I went to fix that.
I looked at the Huffington Post article. It does not make the claim.
I sat through the first five minutes of the first video. I got as far as seeing some guy who saw some performance art, and didn't like it, and was posting a review.
I sat through the first three minutes of the second video. The closest I got to an actual claim was that there are Illuminati symbolism. Note: Illuminati ≠ Satanic, and referring to satanic symbols (or symbols that have cultural associations with Satanism) doesn't make it a satanic religious practice.
I sat through 30 seconds of the last video. I assume the claims came later. I had already committed far too much time to a poor question, and I stopped.
The question should be edited to quote an actual, specific, claim that someone believes.
The question was originally closed by Sklivvz as too vague. He's still right. When does a figure with wings become an angel? When does an angel symbolise something satanic? When does a performance with satanic themes become a satanic ritual?