You can take it back even further to the Archudke’s assassin just bumping into him deciding to get a sandwich. One man’s need for lunch 100 years ago gave rise to tentacle porn half the world away. What a world.
Is anybody going to explain?
No? Okay.
1. Archduke Ferndinand is murdered, causing World War 1.
2. The Allies win WW1, imposing the Treaty of Versailles on Germany.
3. This causes tension between Germany and the rest of Europe, something Adolf Hitler takes advantage of and begins WW2.
4. Japan joins the axis in WW2 in order to expand their empire.
5. The Axis is defeated, and Japan comes under US occupation.
6. American soldiers bring comic books, cartoons, and other American mediums to Japan which stay behind even after the occupation is over.
7. Post-WW2 Japan imposes strict censorship laws that include the banning of most conventional porn.
8. Japanese citizens retaliate by drawing comics with women having sex with vaguely penis-shaped objects like tentacles to exploit loopholes in the law.
9. It establishes itself as a fetish even after the laws are relaxed, and so Hentai was born.