Interesting conspiracy theories. Problem is none of these "causes was mentioned in the article. There is no mention of overfilling, O2, Aluminum, heat, or impact. For all we know this was a recently hydroed and "VISed" steel tank, partially filled (to below rated pressure) with an inert gas (like helium or argon), stored in the apartment and gently handled. OK, that would be a little far fetched, but just as unlikely is that it was an aluminum tank of questionable alloy overfilled with 100% Oxygen, stored in a hot location and thrown around.
The article says "cause unknown" To me, that means "cause unknown"