How on earth does a weak dollar stimulate the economy?!

The same way that a strong dollar cripples the economy.
I can see why it would be a little counterintuitive.

In a non-debt based system like stocks or crypto, you want strong assets.
In a debt based system it's exactly the opposite.

If I take out a $500k loan to buy a house or start a business... well then wouldn't it be nice if that debt that I owe was suddenly worth less money, and thus easier to pay back. Meanwhile the asset that I purchased with the liability is going up in value.

So not only do low interest rates mean I personally owe back less money but it also means fiat will flood the ecosystem and make it even easier to pay back the principal. Easy money environments pump risk-on assets like tech stocks and crypto to the moon.

A strong dollar does the opposite of everything I just said. The only people who want a strong dollar are the ones holding dollars (which nobody likes doing because the value is always going down no matter what). Higher interest rates strangle the economy and suck liquidity out of the system.

Hopefully that makes sense.