Why did hitler believe that jews and other subhumans had to be exterminated?

Hitlers Nazi movement believed in a pure race or breed, which is superior to other races. The pure Germanic race or blood was championed as having better qualities. prominent Nazi doctors and scientist posited that the pure race would save the society from several health related costs.

On a closer look of the ideology, it was simply a propaganda that he used to rule over the masses and convince them to join the war and pursue his ambitions.