guessed

Immediately, the fraudsters were caught.

And it was the case in the United States, somewhere in the 1970s, even in the pre-Internet era, when letters were paper. The owner of a large brokerage company (or a dealer, I don’t know exactly – in general, a company that exists at the expense of the difference in rates when buying and selling securities on the stock exchange) comes, among other things, such a letter: “Tomorrow the shares of General Electric will rise.” There is no back address, no signature. I thought the owner was a joke.
But the next day, a letter again came without a back address and a signature: "Tomorrow Procter & Gamble shares will drop." And indeed, the next day they fell. The owner also looked at the summaries for the previous day – then the shares of General Electric rose. It was a shit, the owner thought.
On the third day, a mysterious letter reads, “Ford shares will drop tomorrow.” They have descended!
The owner was intrigued, and when for the fourth time the letter came: “Tomorrow the stock of Boeing will rise,” he risked and that day bought a few shares of Boeing, and the next day with a profit sold them – the prediction came true!
When the letter came for the fifth time, "Tomorrow the Walt Disney shares will fall," he sold the shares that day, and the next day bought them cheaply. The prediction worked like a clock. The owner did not know what to think: he holds a large analytical department, pays his employees good money, and they, frankly, can't predict anything. Here everything is so simple and accurate!
On the sixth day, again a mysterious letter, which the owner was looking forward to: "Tomorrow IBM shares will fall." It all coincided again! He earned again. Some kind of mysticism, the owner thought, but already unconditionally believed in the predictions of the letters.
On the seventh day: “Coca-Cola stocks will rise tomorrow.” The owner invested a lot of money in this operation, but earned a round amount!
On the eighth day again a letter: "Tomorrow the shares of such a company will rise." The owner, not thinking for a long time, for all the free money bought these shares, and... lost everything - the next day the firm announced its liquidation.

Those fraudsters were caught. The last company, of course, turned out to be a one-day, one-day. But how did they guess? and none. They did not guess. Moreover, they did not aim to guess.
The fraudsters took from two thousand addresses, a thousand sent letters where they talked about raising the price of shares, and another thousand - about lowering. If the price of shares increased, then in the future worked only with the first thousand recipients: five hundred letters were sent about the increase, five hundred others - about the decline of shares. and so on. In the end, there were a few people with whom the fraudsters worked specifically.
In general, after 8-9 times of coincidences, people begin to blindly believe in mysticism and all kinds of hell, and you can do anything with them.