I was referring to conspiracy theories in general, not specifically to the USD. I could have been more clear in my text.

But in response to your question, the USD comprised approx 80% of foreign reserves in the 1970s, down to ~70% in 2000, and currently sits around 60% as of 2019.

In addition, since 1450-ish, at various times, a handful of EU countries held the top spot as the primary currency, from Portugal, Spain, the Netherlands, France, to the UK. It's seems inevitable we'll face a similar fate when something else comes along to dethrone the USD. We certainly meet the criteria: overly indebted, waning influence around the world, circus-like politics (on both sides), etc.