but there is no other way to actually show causation. You can't 'look at' causation. You can look at a million chess games, you'll never be able to see the rules themselves. All you see is correlation between how the pieces move in every game and from this you can try to figure the rules out, if any exist at all.

So while weak(!) correlation does not imply causation, strong correlation pretty much does. It's how the scientific method works. We can't look behind the curtain and take a look at the rule sheet.