Yeah, which is why the data is backed up by multiple panel analyses that actually make the argument for causation. The US data shows that crime rates rose like clockwork approximately ~20 years after leaded gasoline is used en masse, and drops ~20 years after it was banned.

Different states introduced and subsequently banned leaded gasoline on different schedules, so this was a 'natural' experiment, unless you can think of some other causative factor that precisely explains the timing of the rise and fall of crime.

I don't understand this content-free 'correlation does not equal causation' argument.

Sure, in the absence of other evidence and a mechanism of action, we should have healthy skepticism, but it's known how lead affects brain development, particularly how it screws up development of the frontal cortex, lowering both intelligence and social inhibition.