[tsimionescu]

Sure, that's a plausible account. However, they would only compete if they appeared in a pretty small geographical area. That still leaves it as being a relatively singular event. Maybe much more than once in a few billion years, but still much rarer than many seem to assume.

I would also note that we don't really know of any mechanism that would require millions of years for chemical reactions, or any equivalent of the theory of evolution that would work for hypothetical complex organic substances. Not to say that either is impossible!