Interesting analysis, and somewhat surprising.

The number of people who finish a multi-chapter fan-fiction is, surprisingly, almost always 40-60% of the number who clicked on the first chapter, with the very best reaching 60%, and the misspelled, grammar-free, plot-free, alphabet-soup-vomit of ten-year-olds retaining about 40%.

Huh, that's unexpected.

perhaps 4,000 readers finished it.

I understand the calculation, but it seems very low, are you sure you haven't missed anything?

So what actually happened was that a moderately-popular fanfiction that had been read by a few thousand people was reported on in a way that misled publishers into thinking that it had millions of readers, when really, it just had an unusually large number of chapters.

If this was enough to get published, Worm would have been by now (not a fanfic, much better story, more readers, active online discussion and fanfic groups, large enough to be serialized into 10+ volumes). Yet from what I understand Wildbow has not had a single editor/publisher approach him yet.

I suspect that, while an inflated number of readers might bring a story to the attention of a decision maker in the publishing business, it is but one of many many factors going into a major decision like publishing a manuscript. 50SoG was simply lucky to get picked up, and lucky to do well. So the "self-fulfilling prophesy" bit is a big stretch.