How did ancient fortune tellers predict a person's death?

Ancient fortune tellers were able to guess a person's death date by using probability questions and some vague rhetoric. Now many people believe in fortune tellers, but some people believe that science will not believe those crooked ways. Because they believe that the world is like this, they should believe in science. Without monsters, there is nothing to save in the sky. But what we want to tell you here is that we really have to believe in science, but if something exists, it has its reason after all, just like some fortune tellers, who can guess how old you can live, what you should and should not do in your daily life, or it will bring you bad luck. Next, I will explain it carefully for you.

Ancient fortune tellers were able to guess a person's date of death and used vague rhetoric. For example, if you ask a fortune teller some questions, he always asks you a few questions first and tells you that you are not in the state recently. No matter who asks you about it, you must say that it is right. After all, as a person, there must be some minor physical problems that make you happy. Then he approaches step by step, and finally you reveal the answer yourself. Moreover, if you want to predict your life span, he will only give you a vague statement. You can live to be 80 years old, or you can only live to be 70 years old, and you will be given a condition that you must cross a hurdle when you are 20 or 30 years old, so that you can safely live to be 60 or 70 years old.

Fortune tellers can guess a person's date of death because they use the question of probability. I need to give you another example. When three people apply for a university, they will ask a fortune teller who can get in. At this time, the fortune teller will output a thumb, indicating one. If a person is admitted. The fortune teller is right. If two people pass the exam, then one means that one person fails. If three people are admitted, then one is admitted together.

If you have any good ideas about this problem, please write them in the comments and discuss them together.