If you ask specialists about their backgrounds you will find that they took different paths. The critical step is time in the speciality, not background. For any job there's never a pool of applicants who are pretrained for that exact job, everyone takes time to get up to speed. People from related fields do just as well learning job tasks. The labor market is fluid if properly incentivized. Commenters intentionally pretend not to understand because they want cheap labor and want to impoverish the American worker.