"Brain Drain" has been a thing for years. I can remember in the late 90s in my Developmental Econ class my Peruvian professor complaining of brain drain from Latin America and how loss of top tier talent affected economic growth. We all appreciated the irony since she herself was a part of the issue she complained about, having studied and taught in the US for quite some time as she was standing up there saying this to us. But I could see her point.