star trek - Since Kirk found Khan much later in the series, how did he get revived early in the movie?

Admiral Marcus says that after the destruction of Vulcan they started exploring deeper into space and found the Botany Bay with the cryogenically frozen Augments. They revived Khan hoping to use his superior intellect to help them design weapons to protect against powerful enemies such as Nero, using his crew as leverage.

Had the timeline not been altered by Nero in the first movie, the Botany Bay would have remained undiscovered in deep space until the Enterprise found it later, as shown in the TOS episode "Space Seed."