So let's just say if there is a small economy where there are only two investors you and Elon Musk, and you decide to skip investing in any business and hide money under the mattress, then this is equivalent of you giving the money to Elon Musk to invest in his business. How? Because now you're not competing him for raw materials, labor and capital.
Then when he built self-driving cars and economic growth happens because of this productive activity, when you take your money out of your mattress it is now worth more , and I'm presuming no new dollars were produced and this time.
You can see the effect if a major stockholder of a company decides to not participate in the functioning of the company, this in effect is equivalent of him lending his stocks to the other stockholders. This does not mean that somehow the company is working at a reduced power.