How can chess computers be programmed so that it can be so accurately adjusted to a skill level ranging from a beginner to a grandmaster?

They are artificially intelligent. They watch thousands of hours of videos of the game they are going to play. After they learn, they challenge themselves against themselves and save all the moves it used that time, they play another game against the saved game and if they best it then they save the new and repeat. I am not sure about this because I am just a 15 yr old but the early ones brute forced the game and one. Brute Forcing is a way to try out every possible move and pick the most like to succeed or the most efficient one, brute force is also used in hacking or cracking passwords that have something in common. Like let's say ur password is Jakeis35. I would make a list that would be:
Jake
jake
Is
is
35
34

and with a software it will put together every possible pair and will stop when it matches the password on the server or if the password let it login.