ELI5: How did the 1929 crisis happen?

Imagine everyone in your street loves collecting Pokemon cards.

1. Everyone's buying cards: People think Pokemon cards will only go up in value, so everyone starts buying them, even if they don't really want them or can't really afford them. Some people even borrow money from the bank to buy more cards!

1. Card factories working overtime: Because everyone's buying, the card factories (companies) are printing tons of cards. They hire more people and build more factories. This is good, right? Not really...

1. Prices get too high: Because everyone wants cards, the price of even ordinary cards goes way, way up. A card that used to cost $1 now costs $10! Some people start to think the prices are too high.

1. People start selling: Some clever kids realize the prices are crazy and start selling their cards to make a profit.

1. Uh oh, prices start falling: When lots of people start selling, the price of cards goes down. Suddenly, those $10 cards are worth $8, then $6, then $4!

1. Panic selling!: Everyone gets scared that their cards will be worthless, so they all try to sell at the same time. The price crashes!

1. Card factories close: Because nobody's buying, the card factories have to close down. People lose their jobs.

1. People can't pay back the bank: Remember those people who borrowed money to buy cards? Now their cards are worthless and they can't pay the bank back. The bank gets in trouble too!