Yes, coincidence. It was submitted for publication but rejected in 1863 (and then lost in a pile of papers and re-found in 1989). Anybody familiar with e.g. how most of Tolkien’s works were published posthumously won’t be surprised. Jules Verne wrote a lot, and he did not have a Christopher to comb through the boxes of papers he left. There are 200k pages of drafts, letters and manuscripts in a museum in Nantes, and not everything ended up there.

And I don’t see why the Internet is relevant: not everything that happened since the mid-1980s are internet-related conspiracies.