There is a mathematical probability problem that I can't understand.

According to him, if the first three people are all drawn, isn't the probability of the last person zero?

These are two questions. The probability of five people drawing three seats is the same, but if you want to ask "the probability of the first person drawing the last person", it becomes the probability of four people drawing two seats, which is 50%.

That is to say, in the lottery, if we don't know the result of the previous lottery, then the probability of winning the prize for all people should be the same.