the only thing the "prophecies" indicated was that a mega powered sunhumma bitch would arrive on the planet earth. it doesn't state that he would be alone or abandoned or anything more specific. thus, its possible kryptonians not only explored other planets in the universe, but eventually planned on colonizing them. remember, any kryptonian would be a super powered badass on earth.
however, once doom started hitting krypton, and things became desperate, jor-el had only enough time to send his son on his way. he targetted earth because he had already explored and OK'd it.
the natives' prophecies are fulfilled by clark being there, just as much as they would be if jor-el and 10 subordinates were there.
