You're confusing two different things. What was initially claimed:
> gold hoarding caused the economy to collapse in 1929
This makes it sound like gold caused the economy to collapse.
But your quote is referring to the Great Depression spreading world wide, so it's quite different. Don't think there is any definite and agree-upon source of what caused the Great Depression, many things interacting together for sure. You can't say that gold hoarding caused the economy to collapse though.
Sure people came up with all kinds of explanations but the most accepted ones speak of deficient Aggregate Demand. Low aggregate demand can almost tautologically be seen as the flip side of too high demand for currency.
"We buy newly-produced goods with money. A Keynesian recession is an excess supply of newly-produced goods, and a deficiency of Aggregate Demand. In a monetary exchange economy, a deficiency of Aggregate Demand, and an excess supply of goods, is an excess demand for money. Money is what we demand goods with."
> gold hoarding caused the economy to collapse in 1929
This makes it sound like gold caused the economy to collapse.
But your quote is referring to the Great Depression spreading world wide, so it's quite different. Don't think there is any definite and agree-upon source of what caused the Great Depression, many things interacting together for sure. You can't say that gold hoarding caused the economy to collapse though.