Demand is created by offering things that people want.
If the people need a device for all of the various and sundry functions and there is none, the demand is still there, but the purchases are not being made.
In the 90's, that unknown device was the personal computer. When the device was created, not really much demand. There was no "killer app".
However, then the suite of Microsoft programs came into being and presto, there was demand. The demand created the purchasing and the purchasing fired up the economy and the upward thrust of the economy was begun by the demand that produced the production that added more money to the consumers and the wealth spread across the economy.
Obviously, the same thing happens whether the boom starts in the tech sector of the energy sector or the transportation actor.
If tomorrow, an engine was produced that powered vehicles on hydrogen harvested from the air that produced clean, fresh water as the exhaust, every car owner, fleet owner and hobbyist would want one and the economic boom would make the 90's look like the 30's.
If the product exists to create the demand, the money to buy the product will appear as if by magic.
Even if the money is available in great quantity to buy a product that does not exist, no purchase will be made.